diff --git a/.github/workflows/pylint.yml b/.github/workflows/pylint.yml
new file mode 100644
index 0000000..9613649
--- /dev/null
+++ b/.github/workflows/pylint.yml
@@ -0,0 +1,26 @@
+name: Pylint
+
+on: [push]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.8", "3.9", "3.10"]
+    steps:
+    - uses: actions/checkout@v4
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v3
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: Set up Python path
+      run: echo "PYTHONPATH=$PWD" >> $GITHUB_ENV
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install pylint
+        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
+    - name: Analysing the code with pylint
+      run: |
+        pylint $(git ls-files '*.py')
diff --git a/.pylintrc b/.pylintrc
new file mode 100644
index 0000000..bbaa833
--- /dev/null
+++ b/.pylintrc
@@ -0,0 +1,627 @@
+[MAIN]
+
+# Analyse import fallback blocks. This can be used to support both Python 2 and
+# 3 compatible code, which means that the block might have code that exists
+# only in one or another interpreter, leading to false positives when analysed.
+analyse-fallback-blocks=no
+
+# Clear in-memory caches upon conclusion of linting. Useful if running pylint
+# in a server-like mode.
+clear-cache-post-run=no
+
+# Load and enable all available extensions. Use --list-extensions to see a list
+# all available extensions.
+#enable-all-extensions=
+
+# In error mode, messages with a category besides ERROR or FATAL are
+# suppressed, and no reports are done by default. Error mode is compatible with
+# disabling specific errors.
+#errors-only=
+
+# Always return a 0 (non-error) status code, even if lint errors are found.
+# This is primarily useful in continuous integration scripts.
+#exit-zero=
+
+# A comma-separated list of package or module names from where C extensions may
+# be loaded. Extensions are loading into the active Python interpreter and may
+# run arbitrary code.
+extension-pkg-allow-list=
+
+# A comma-separated list of package or module names from where C extensions may
+# be loaded. Extensions are loading into the active Python interpreter and may
+# run arbitrary code. (This is an alternative name to extension-pkg-allow-list
+# for backward compatibility.)
+extension-pkg-whitelist=
+
+# Return non-zero exit code if any of these messages/categories are detected,
+# even if score is above --fail-under value. Syntax same as enable. Messages
+# specified are enabled, while categories only check already-enabled messages.
+fail-on=
+
+# Specify a score threshold under which the program will exit with error.
+fail-under=10
+
+# Interpret the stdin as a python script, whose filename needs to be passed as
+# the module_or_package argument.
+#from-stdin=
+
+# Files or directories to be skipped. They should be base names, not paths.
+ignore=CVS
+
+# Add files or directories matching the regular expressions patterns to the
+# ignore-list. The regex matches against paths and can be in Posix or Windows
+# format. Because '\\' represents the directory delimiter on Windows systems,
+# it can't be used as an escape character.
+ignore-paths=
+
+# Files or directories matching the regular expression patterns are skipped.
+# The regex matches against base names, not paths. The default value ignores
+# Emacs file locks
+ignore-patterns=^\.#
+
+# List of module names for which member attributes should not be checked
+# (useful for modules/projects where namespaces are manipulated during runtime
+# and thus existing member attributes cannot be deduced by static analysis). It
+# supports qualified module names, as well as Unix pattern matching.
+ignored-modules=
+
+# Python code to execute, usually for sys.path manipulation such as
+# pygtk.require().
+#init-hook=
+
+# Use multiple processes to speed up Pylint. Specifying 0 will auto-detect the
+# number of processors available to use, and will cap the count on Windows to
+# avoid hangs.
+jobs=1
+
+# Control the amount of potential inferred values when inferring a single
+# object. This can help the performance when dealing with large functions or
+# complex, nested conditions.
+limit-inference-results=100
+
+# List of plugins (as comma separated values of python module names) to load,
+# usually to register additional checkers.
+load-plugins=
+
+# Pickle collected data for later comparisons.
+persistent=yes
+
+# Minimum Python version to use for version dependent checks. Will default to
+# the version used to run pylint.
+py-version=3.12
+
+# Discover python modules and packages in the file system subtree.
+recursive=no
+
+# Add paths to the list of the source roots. Supports globbing patterns. The
+# source root is an absolute path or a path relative to the current working
+# directory used to determine a package namespace for modules located under the
+# source root.
+source-roots=
+
+# When enabled, pylint would attempt to guess common misconfiguration and emit
+# user-friendly hints instead of false-positive error messages.
+suggestion-mode=yes
+
+# Allow loading of arbitrary C extensions. Extensions are imported into the
+# active Python interpreter and may run arbitrary code.
+unsafe-load-any-extension=no
+
+# In verbose mode, extra non-checker-related info will be displayed.
+#verbose=
+
+
+[BASIC]
+
+# Naming style matching correct argument names.
+argument-naming-style=snake_case
+
+# Regular expression matching correct argument names. Overrides argument-
+# naming-style. If left empty, argument names will be checked with the set
+# naming style.
+#argument-rgx=
+
+# Naming style matching correct attribute names.
+attr-naming-style=snake_case
+
+# Regular expression matching correct attribute names. Overrides attr-naming-
+# style. If left empty, attribute names will be checked with the set naming
+# style.
+#attr-rgx=
+
+# Bad variable names which should always be refused, separated by a comma.
+bad-names=foo,
+          bar,
+          baz,
+          toto,
+          tutu,
+          tata
+
+# Bad variable names regexes, separated by a comma. If names match any regex,
+# they will always be refused
+bad-names-rgxs=
+
+# Naming style matching correct class attribute names.
+class-attribute-naming-style=any
+
+# Regular expression matching correct class attribute names. Overrides class-
+# attribute-naming-style. If left empty, class attribute names will be checked
+# with the set naming style.
+#class-attribute-rgx=
+
+# Naming style matching correct class constant names.
+class-const-naming-style=UPPER_CASE
+
+# Regular expression matching correct class constant names. Overrides class-
+# const-naming-style. If left empty, class constant names will be checked with
+# the set naming style.
+#class-const-rgx=
+
+# Naming style matching correct class names.
+class-naming-style=PascalCase
+
+# Regular expression matching correct class names. Overrides class-naming-
+# style. If left empty, class names will be checked with the set naming style.
+#class-rgx=
+
+# Naming style matching correct constant names.
+const-naming-style=UPPER_CASE
+
+# Regular expression matching correct constant names. Overrides const-naming-
+# style. If left empty, constant names will be checked with the set naming
+# style.
+#const-rgx=
+
+# Minimum line length for functions/classes that require docstrings, shorter
+# ones are exempt.
+docstring-min-length=-1
+
+# Naming style matching correct function names.
+function-naming-style=snake_case
+
+# Regular expression matching correct function names. Overrides function-
+# naming-style. If left empty, function names will be checked with the set
+# naming style.
+#function-rgx=
+
+# Good variable names which should always be accepted, separated by a comma.
+good-names=i,
+           j,
+           k,
+           ex,
+           Run,
+           _
+
+# Good variable names regexes, separated by a comma. If names match any regex,
+# they will always be accepted
+good-names-rgxs=
+
+# Include a hint for the correct naming format with invalid-name.
+include-naming-hint=no
+
+# Naming style matching correct inline iteration names.
+inlinevar-naming-style=any
+
+# Regular expression matching correct inline iteration names. Overrides
+# inlinevar-naming-style. If left empty, inline iteration names will be checked
+# with the set naming style.
+#inlinevar-rgx=
+
+# Naming style matching correct method names.
+method-naming-style=snake_case
+
+# Regular expression matching correct method names. Overrides method-naming-
+# style. If left empty, method names will be checked with the set naming style.
+#method-rgx=
+
+# Naming style matching correct module names.
+module-naming-style=snake_case
+
+# Regular expression matching correct module names. Overrides module-naming-
+# style. If left empty, module names will be checked with the set naming style.
+#module-rgx=
+
+# Colon-delimited sets of names that determine each other's naming style when
+# the name regexes allow several styles.
+name-group=
+
+# Regular expression which should only match function or class names that do
+# not require a docstring.
+no-docstring-rgx=^_
+
+# List of decorators that produce properties, such as abc.abstractproperty. Add
+# to this list to register other decorators that produce valid properties.
+# These decorators are taken in consideration only for invalid-name.
+property-classes=abc.abstractproperty
+
+# Regular expression matching correct type alias names. If left empty, type
+# alias names will be checked with the set naming style.
+#typealias-rgx=
+
+# Regular expression matching correct type variable names. If left empty, type
+# variable names will be checked with the set naming style.
+#typevar-rgx=
+
+# Naming style matching correct variable names.
+variable-naming-style=snake_case
+
+# Regular expression matching correct variable names. Overrides variable-
+# naming-style. If left empty, variable names will be checked with the set
+# naming style.
+#variable-rgx=
+
+
+[CLASSES]
+
+# Warn about protected attribute access inside special methods
+check-protected-access-in-special-methods=no
+
+# List of method names used to declare (i.e. assign) instance attributes.
+defining-attr-methods=__init__,
+                      __new__,
+                      setUp,
+                      asyncSetUp,
+                      __post_init__
+
+# List of member names, which should be excluded from the protected access
+# warning.
+exclude-protected=_asdict,_fields,_replace,_source,_make,os._exit
+
+# List of valid names for the first argument in a class method.
+valid-classmethod-first-arg=cls
+
+# List of valid names for the first argument in a metaclass class method.
+valid-metaclass-classmethod-first-arg=mcs
+
+
+[DESIGN]
+
+# List of regular expressions of class ancestor names to ignore when counting
+# public methods (see R0903)
+exclude-too-few-public-methods=
+
+# List of qualified class names to ignore when counting class parents (see
+# R0901)
+ignored-parents=
+
+# Maximum number of arguments for function / method.
+max-args=5
+
+# Maximum number of attributes for a class (see R0902).
+max-attributes=7
+
+# Maximum number of boolean expressions in an if statement (see R0916).
+max-bool-expr=5
+
+# Maximum number of branch for function / method body.
+max-branches=12
+
+# Maximum number of locals for function / method body.
+max-locals=15
+
+# Maximum number of parents for a class (see R0901).
+max-parents=7
+
+# Maximum number of public methods for a class (see R0904).
+max-public-methods=20
+
+# Maximum number of return / yield for function / method body.
+max-returns=6
+
+# Maximum number of statements in function / method body.
+max-statements=50
+
+# Minimum number of public methods for a class (see R0903).
+min-public-methods=2
+
+
+[EXCEPTIONS]
+
+# Exceptions that will emit a warning when caught.
+overgeneral-exceptions=builtins.BaseException,builtins.Exception
+
+
+[FORMAT]
+
+# Expected format of line ending, e.g. empty (any line ending), LF or CRLF.
+expected-line-ending-format=
+
+# Regexp for a line that is allowed to be longer than the limit.
+ignore-long-lines=^\s*(# )?<?https?://\S+>?$
+
+# Number of spaces of indent required inside a hanging or continued line.
+indent-after-paren=4
+
+# String used as indentation unit. This is usually "    " (4 spaces) or "\t" (1
+# tab).
+indent-string='    '
+
+# Maximum number of characters on a single line.
+max-line-length=100
+
+# Maximum number of lines in a module.
+max-module-lines=1000
+
+# Allow the body of a class to be on the same line as the declaration if body
+# contains single statement.
+single-line-class-stmt=no
+
+# Allow the body of an if to be on the same line as the test if there is no
+# else.
+single-line-if-stmt=no
+
+
+[IMPORTS]
+
+# List of modules that can be imported at any level, not just the top level
+# one.
+allow-any-import-level=
+
+# Allow explicit reexports by alias from a package __init__.
+allow-reexport-from-package=no
+
+# Allow wildcard imports from modules that define __all__.
+allow-wildcard-with-all=no
+
+# Deprecated modules which should not be used, separated by a comma.
+deprecated-modules=
+
+# Output a graph (.gv or any supported image format) of external dependencies
+# to the given file (report RP0402 must not be disabled).
+ext-import-graph=
+
+# Output a graph (.gv or any supported image format) of all (i.e. internal and
+# external) dependencies to the given file (report RP0402 must not be
+# disabled).
+import-graph=
+
+# Output a graph (.gv or any supported image format) of internal dependencies
+# to the given file (report RP0402 must not be disabled).
+int-import-graph=
+
+# Force import order to recognize a module as part of the standard
+# compatibility libraries.
+known-standard-library=
+
+# Force import order to recognize a module as part of a third party library.
+known-third-party=enchant
+
+# Couples of modules and preferred modules, separated by a comma.
+preferred-modules=
+
+
+[LOGGING]
+
+# The type of string formatting that logging methods do. `old` means using %
+# formatting, `new` is for `{}` formatting.
+logging-format-style=old
+
+# Logging modules to check that the string format arguments are in logging
+# function parameter format.
+logging-modules=logging
+
+
+[MESSAGES CONTROL]
+
+# Only show warnings with the listed confidence levels. Leave empty to show
+# all. Valid levels: HIGH, CONTROL_FLOW, INFERENCE, INFERENCE_FAILURE,
+# UNDEFINED.
+confidence=HIGH,
+           CONTROL_FLOW,
+           INFERENCE,
+           INFERENCE_FAILURE,
+           UNDEFINED
+
+# Disable the message, report, category or checker with the given id(s). You
+# can either give multiple identifiers separated by comma (,) or put this
+# option multiple times (only on the command line, not in the configuration
+# file where it should appear only once). You can also use "--disable=all" to
+# disable everything first and then re-enable specific checks. For example, if
+# you want to run only the similarities checker, you can use "--disable=all
+# --enable=similarities". If you want to run only the classes checker, but have
+# no Warning level messages displayed, use "--disable=all --enable=classes
+# --disable=W".
+disable=R,I,W,
+        logging-fstring-interpolation,
+
+
+# Enable the message, report, category or checker with the given id(s). You can
+# either give multiple identifier separated by comma (,) or put this option
+# multiple time (only on the command line, not in the configuration file where
+# it should appear only once). See also the "--disable" option for examples.
+enable=
+
+
+[METHOD_ARGS]
+
+# List of qualified names (i.e., library.method) which require a timeout
+# parameter e.g. 'requests.api.get,requests.api.post'
+timeout-methods=requests.api.delete,requests.api.get,requests.api.head,requests.api.options,requests.api.patch,requests.api.post,requests.api.put,requests.api.request
+
+
+[MISCELLANEOUS]
+
+# List of note tags to take in consideration, separated by a comma.
+notes=FIXME,
+      XXX,
+      TODO
+
+# Regular expression of note tags to take in consideration.
+notes-rgx=
+
+
+[REFACTORING]
+
+# Maximum number of nested blocks for function / method body
+max-nested-blocks=5
+
+# Complete name of functions that never returns. When checking for
+# inconsistent-return-statements if a never returning function is called then
+# it will be considered as an explicit return statement and no message will be
+# printed.
+never-returning-functions=sys.exit,argparse.parse_error
+
+
+[REPORTS]
+
+# Python expression which should return a score less than or equal to 10. You
+# have access to the variables 'fatal', 'error', 'warning', 'refactor',
+# 'convention', and 'info' which contain the number of messages in each
+# category, as well as 'statement' which is the total number of statements
+# analyzed. This score is used by the global evaluation report (RP0004).
+evaluation=max(0, 0 if fatal else 10.0 - ((float(5 * error + warning + refactor + convention) / statement) * 10))
+
+# Template used to display messages. This is a python new-style format string
+# used to format the message information. See doc for all details.
+msg-template=
+
+# Set the output format. Available formats are: text, parseable, colorized,
+# json2 (improved json format), json (old json format) and msvs (visual
+# studio). You can also give a reporter class, e.g.
+# mypackage.mymodule.MyReporterClass.
+#output-format=
+
+# Tells whether to display a full report or only the messages.
+reports=no
+
+# Activate the evaluation score.
+score=yes
+
+
+[SIMILARITIES]
+
+# Comments are removed from the similarity computation
+ignore-comments=yes
+
+# Docstrings are removed from the similarity computation
+ignore-docstrings=yes
+
+# Imports are removed from the similarity computation
+ignore-imports=yes
+
+# Signatures are removed from the similarity computation
+ignore-signatures=yes
+
+# Minimum lines number of a similarity.
+min-similarity-lines=4
+
+
+[SPELLING]
+
+# Limits count of emitted suggestions for spelling mistakes.
+max-spelling-suggestions=4
+
+# Spelling dictionary name. No available dictionaries : You need to install
+# both the python package and the system dependency for enchant to work.
+spelling-dict=
+
+# List of comma separated words that should be considered directives if they
+# appear at the beginning of a comment and should not be checked.
+spelling-ignore-comment-directives=fmt: on,fmt: off,noqa:,noqa,nosec,isort:skip,mypy:
+
+# List of comma separated words that should not be checked.
+spelling-ignore-words=
+
+# A path to a file that contains the private dictionary; one word per line.
+spelling-private-dict-file=
+
+# Tells whether to store unknown words to the private dictionary (see the
+# --spelling-private-dict-file option) instead of raising a message.
+spelling-store-unknown-words=no
+
+
+[STRING]
+
+# This flag controls whether inconsistent-quotes generates a warning when the
+# character used as a quote delimiter is used inconsistently within a module.
+check-quote-consistency=no
+
+# This flag controls whether the implicit-str-concat should generate a warning
+# on implicit string concatenation in sequences defined over several lines.
+check-str-concat-over-line-jumps=no
+
+
+[TYPECHECK]
+
+# List of decorators that produce context managers, such as
+# contextlib.contextmanager. Add to this list to register other decorators that
+# produce valid context managers.
+contextmanager-decorators=contextlib.contextmanager
+
+# List of members which are set dynamically and missed by pylint inference
+# system, and so shouldn't trigger E1101 when accessed. Python regular
+# expressions are accepted.
+generated-members=
+
+# Tells whether to warn about missing members when the owner of the attribute
+# is inferred to be None.
+ignore-none=yes
+
+# This flag controls whether pylint should warn about no-member and similar
+# checks whenever an opaque object is returned when inferring. The inference
+# can return multiple potential results while evaluating a Python object, but
+# some branches might not be evaluated, which results in partial inference. In
+# that case, it might be useful to still emit no-member and other checks for
+# the rest of the inferred objects.
+ignore-on-opaque-inference=yes
+
+# List of symbolic message names to ignore for Mixin members.
+ignored-checks-for-mixins=no-member,
+                          not-async-context-manager,
+                          not-context-manager,
+                          attribute-defined-outside-init
+
+# List of class names for which member attributes should not be checked (useful
+# for classes with dynamically set attributes). This supports the use of
+# qualified names.
+ignored-classes=optparse.Values,thread._local,_thread._local,argparse.Namespace
+
+# Show a hint with possible names when a member name was not found. The aspect
+# of finding the hint is based on edit distance.
+missing-member-hint=yes
+
+# The minimum edit distance a name should have in order to be considered a
+# similar match for a missing member name.
+missing-member-hint-distance=1
+
+# The total number of similar names that should be taken in consideration when
+# showing a hint for a missing member.
+missing-member-max-choices=1
+
+# Regex pattern to define which classes are considered mixins.
+mixin-class-rgx=.*[Mm]ixin
+
+# List of decorators that change the signature of a decorated function.
+signature-mutators=
+
+
+[VARIABLES]
+
+# List of additional names supposed to be defined in builtins. Remember that
+# you should avoid defining new builtins when possible.
+additional-builtins=
+
+# Tells whether unused global variables should be treated as a violation.
+allow-global-unused-variables=yes
+
+# List of names allowed to shadow builtins
+allowed-redefined-builtins=
+
+# List of strings which can identify a callback function by name. A callback
+# name must start or end with one of those strings.
+callbacks=cb_,
+          _cb
+
+# A regular expression matching the name of dummy variables (i.e. expected to
+# not be used).
+dummy-variables-rgx=_+$|(_[a-zA-Z0-9_]*[a-zA-Z0-9]+?$)|dummy|^ignored_|^unused_
+
+# Argument names that match this expression will be ignored.
+ignored-argument-names=_.*|^ignored_|^unused_
+
+# Tells whether we should check for unused import in __init__ files.
+init-import=no
+
+# List of qualified module names which can have objects that can redefine
+# builtins.
+redefining-builtins-modules=six.moves,past.builtins,future.builtins,builtins,io
diff --git a/lshell/builtins.py b/lshell/builtincmd.py
similarity index 78%
rename from lshell/builtins.py
rename to lshell/builtincmd.py
index 054ab3d..a1f55f5 100644
--- a/lshell/builtins.py
+++ b/lshell/builtincmd.py
@@ -1,22 +1,4 @@
-#
-#  Limited command Shell (lshell)
-#
-#  Copyright (C) 2008-2024 Ignace Mouzannar <ghantoos@ghantoos.org>
-#
-#  This file is part of lshell
-#
-#  This program is free software: you can redistribute it and/or modify
-#  it under the terms of the GNU General Public License as published by
-#  the Free Software Foundation, either version 3 of the License, or
-#  (at your option) any later version.
-#
-#  This program is distributed in the hope that it will be useful,
-#  but WITHOUT ANY WARRANTY; without even the implied warranty of
-#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-#  GNU General Public License for more details.
-#
-#  You should have received a copy of the GNU General Public License
-#  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+""" This module contains the built-in commands of lshell """
 
 import glob
 import sys
@@ -54,9 +36,9 @@ def lsudo(conf):
         for command in conf["sudo_commands"]:
             sys.stdout.write(f" - {command}\n")
         return 0
-    else:
-        sys.stdout.write("No sudo commands allowed\n")
-        return 1
+
+    sys.stdout.write("No sudo commands allowed\n")
+    return 1
 
 
 def history(conf, log):
@@ -67,11 +49,11 @@ def history(conf, log):
         except IOError:
             log.error(f"WARN: couldn't write history to file {conf['history_file']}\n")
             return 1
-        f = open(conf["history_file"], "r")
-        i = 1
-        for item in f.readlines():
-            sys.stdout.write(f"{i}:  {item}")
-            i += 1
+        with open(conf["history_file"], "r", encoding="utf-8") as f:
+            i = 1
+            for item in f.readlines():
+                sys.stdout.write(f"{i}:  {item}")
+                i += 1
     except (OSError, IOError, FileNotFoundError) as e:  # Catch specific exceptions
         log.critical(f"** Unable to read the history file: {e}")
         return 1
diff --git a/lshell/checkconfig.py b/lshell/checkconfig.py
index ae7105b..53dc745 100644
--- a/lshell/checkconfig.py
+++ b/lshell/checkconfig.py
@@ -1,22 +1,4 @@
-#
-#  Limited command Shell (lshell)
-#
-#  Copyright (C) 2008-2024 Ignace Mouzannar <ghantoos@ghantoos.org>
-#
-#  This file is part of lshell
-#
-#  This program is free software: you can redistribute it and/or modify
-#  it under the terms of the GNU General Public License as published by
-#  the Free Software Foundation, either version 3 of the License, or
-#  (at your option) any later version.
-#
-#  This program is distributed in the hope that it will be useful,
-#  but WITHOUT ANY WARRANTY; without even the implied warranty of
-#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-#  GNU General Public License for more details.
-#
-#  You should have received a copy of the GNU General Public License
-#  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+""" This module contains the checkconfig class of lshell """
 
 import sys
 import os
@@ -29,12 +11,12 @@
 import grp
 import time
 import glob
+from logging.handlers import SysLogHandler
 
 # import lshell specifics
 from lshell import utils
 from lshell import variables
-from lshell import sec
-from lshell import builtins
+from lshell.builtincmd import export
 
 
 class CheckConfig:
@@ -69,18 +51,16 @@ def __init__(self, args, refresh=None, stdin=None, stdout=None, stderr=None):
         self.check_user_integrity()
         self.get_config_user()
         self.check_env()
-        self.check_scp_sftp()
         self.set_noexec()
 
     def check_config_file_exists(self, configfile):
         """Check if the configuration file exists, else exit with error"""
         if not os.path.exists(configfile):
             self.stderr.write("Error: Config file doesn't exist\n")
-            self.stderr.write(variables.usage)
-            sys.exit(1)
+            utils.usage()
 
     def check_script(self):
-        # Check if lshell is invoked with the correct binary and script extension
+        """Check if lshell is invoked with the correct binary and script extension"""
         if sys.argv[0].endswith("bin/lshell") and sys.argv[-1].endswith(".lsh"):
             script_path = os.path.realpath(sys.argv[-1])
             self.log.debug(f"Detected script mode: {script_path}")
@@ -115,7 +95,7 @@ def getoptions(self, arguments, conf):
             if option in ["-c"]:
                 conf["ssh"] = value
             if option in ["-h", "--help"]:
-                utils.usage()
+                utils.usage(exitcode=0)
             if option in ["--version"]:
                 utils.version()
 
@@ -145,10 +125,10 @@ def check_env(self):
             for envfile in self.conf["env_vars_files"]:
                 file_path = os.path.expandvars(envfile)
                 try:
-                    with open(file_path) as env_vars:
+                    with open(file_path, encoding="utf-8") as env_vars:
                         for env_var in env_vars.readlines():
                             if env_var.split(" ", 1)[0] == "export":
-                                builtins.export(env_var.strip())
+                                export(env_var.strip())
                 except (OSError, IOError):
                     self.stderr.write(
                         f"ERROR: Unable to read environment file: {file_path}\n"
@@ -160,8 +140,7 @@ def check_file(self, file):
         """
         if not os.path.exists(file):
             self.stderr.write("Error: Config file doesn't exist\n")
-            self.stderr.write(variables.usage)
-            sys.exit(1)
+            utils.usage()
         else:
             self.config = configparser.ConfigParser()
 
@@ -195,11 +174,12 @@ def check_log(self):
         }
 
         # create logger for lshell application
-        if "syslogname" in self.conf:
+        if self.conf.get("syslogname"):
             try:
-                logname = eval(self.conf["syslogname"])
+                logname = str(self.conf["syslogname"])
             except (SyntaxError, NameError, TypeError):
-                logname = self.conf["syslogname"]
+                sys.stderr.write("ERR: syslogname must be a string\n")
+                sys.exit(1)
         else:
             logname = "lshell"
 
@@ -209,15 +189,15 @@ def check_log(self):
         # this is useful if configuration is reloaded
         for loghandler in logger.handlers:
             try:
-                logging.shutdown(logger.handlers)
+                logging.shutdown(loghandler)
             except TypeError:
                 pass
         for logfilter in logger.filters:
             logger.removeFilter(logfilter)
 
-        formatter = logging.Formatter("%%(asctime)s (%s): %%(message)s" % getuser())
+        formatter = logging.Formatter(f"%(asctime)s ({getuser()}): %(message)s")
         syslogformatter = logging.Formatter(
-            "%s[%s]: %s: %%(message)s" % (logname, os.getpid(), getuser())
+            f"{logname}[{os.getpid()}]: {getuser()}: %(message)s"
         )
 
         logger.setLevel(logging.DEBUG)
@@ -241,17 +221,18 @@ def check_log(self):
             self.conf["loglevel"] = 0
 
         # read logfilename is exists, and set logfilename
-        if "logfilename" in self.conf:
+        if self.conf.get("logfilename"):
             try:
-                logfilename = eval(self.conf["logfilename"])
+                logfilename = str(self.conf["logfilename"])
             except (SyntaxError, NameError, TypeError):
-                logfilename = self.conf["logfilename"]
+                sys.stderr.write("ERR: logfilename must be a string\n")
+                sys.exit(1)
             currentime = time.localtime()
-            logfilename = logfilename.replace("%y", "%s" % currentime[0])
-            logfilename = logfilename.replace("%m", "%02d" % currentime[1])
-            logfilename = logfilename.replace("%d", "%02d" % currentime[2])
+            logfilename = logfilename.replace("%y", f"{currentime[0]}")
+            logfilename = logfilename.replace("%m", f"{currentime[1]:02d}")
+            logfilename = logfilename.replace("%d", f"{currentime[2]:02d}")
             logfilename = logfilename.replace(
-                "%h", "%02d%02d" % (currentime[3], currentime[4])
+                "%h", f"{currentime[3]:02d}{currentime[4]:02d}"
             )
             logfilename = logfilename.replace("%u", getuser())
         else:
@@ -260,8 +241,6 @@ def check_log(self):
         if self.conf["loglevel"] > 0:
             try:
                 if logfilename == "syslog":
-                    from logging.handlers import SysLogHandler
-
                     syslog = SysLogHandler(address="/dev/log")
                     syslog.setFormatter(syslogformatter)
                     syslog.setLevel(self.levels[self.conf["loglevel"]])
@@ -270,8 +249,8 @@ def check_log(self):
                     # if log file is writable add new log file handler
                     logfile = os.path.join(self.conf["logpath"], logfilename + ".log")
                     # create log file if it does not exist, and set permissions
-                    fp = open(logfile, "a")
-                    fp.close()
+                    with open(logfile, "a", encoding="utf-8"):
+                        pass
                     try:
                         os.chmod(logfile, 0o600)
                     except OSError:
@@ -299,8 +278,6 @@ def get_config(self):
 
         # list the include_dir directory and read configuration files
         if "include_dir" in self.conf:
-            import glob
-
             self.conf["include_dir_conf"] = glob.glob(f"{self.conf['include_dir']}*")
             self.config.read(self.conf["include_dir_conf"])
 
@@ -369,7 +346,7 @@ def get_config_sub(self, section):
                             # remove double slashes
                             liste[0] = liste[0].replace("//", "/")
                             self.conf_raw.update({key: str(liste)})
-                        elif stuff and type(eval(stuff)) == list:
+                        elif stuff and isinstance(eval(stuff), list):
                             self.conf_raw.update({key: stuff})
                 # case allowed is set to 'all'
                 elif key == "allowed" and split[0] == "'all'":
@@ -466,7 +443,7 @@ def check_user_integrity(self):
         In case fields are missing, the user is notified and exited from lshell
         """
         for item in variables.required_config:
-            if item not in self.conf_raw.keys():
+            if item not in self.conf_raw:
                 self.log.critical(f"ERROR: Missing parameter '{item}'")
                 self.log.critical(
                     f"ERROR: Add it in the in the [{self.user}] or [default] section of conf file."
@@ -594,7 +571,7 @@ def get_config_user(self):
         if "intro" in self.conf_raw:
             self.conf["intro"] = self.myeval(self.conf_raw["intro"])
         else:
-            self.conf["intro"] = variables.intro
+            self.conf["intro"] = variables.INTRO
 
         if os.path.isdir(self.conf["home_path"]):
             # change dir to home when initially loading the configuration
@@ -617,7 +594,7 @@ def get_config_user(self):
             except (KeyError, SyntaxError, TypeError, NameError):
                 self.log.error(f"CONF: history file error: {self.conf['history_file']}")
         else:
-            self.conf["history_file"] = variables.history_file
+            self.conf["history_file"] = variables.HISTORY_FILE
 
         if not self.conf["history_file"].startswith("/"):
             self.conf["history_file"] = (
@@ -669,117 +646,6 @@ def get_config_user(self):
 
             self.log.error("WinSCP session started")
 
-    def check_scp_sftp(self):
-        """This method checks if the user is trying to SCP a file onto the
-        server. If this is the case, it checks if the user is allowed to use
-        SCP or not, and    acts as requested. : )
-        """
-        if "ssh" in self.conf:
-            if "SSH_CLIENT" in os.environ and "SSH_TTY" not in os.environ:
-
-                # check if sftp is requested and allowed
-                if "sftp-server" in self.conf["ssh"]:
-                    if self.conf["sftp"] == 1:
-                        self.log.error("SFTP connect")
-                        retcode = utils.cmd_parse_execute(self.conf["ssh"])
-                        self.log.error("SFTP disconnect")
-                        sys.exit(retcode)
-                    else:
-                        self.log.error("*** forbidden SFTP connection")
-                        sys.exit(1)
-
-                # initialize cli session
-                from lshell.shellcmd import ShellCmd
-
-                cli = ShellCmd(self.conf, None, None, None, None, self.conf["ssh"])
-                ret_check_path, self.conf = sec.check_path(
-                    self.conf["ssh"], self.conf, ssh=1
-                )
-                if ret_check_path == 1:
-                    self.ssh_warn("path over SSH", self.conf["ssh"])
-
-                # check if scp is requested and allowed
-                if self.conf["ssh"].startswith("scp "):
-                    if self.conf["scp"] == 1 or "scp" in self.conf["overssh"]:
-                        if " -f " in self.conf["ssh"]:
-                            # case scp download is allowed
-                            if self.conf["scp_download"]:
-                                self.log.error(f'SCP: GET "{self.conf["ssh"]}"')
-                            # case scp download is forbidden
-                            else:
-                                self.log.error(
-                                    f'SCP: download forbidden: "{self.conf["ssh"]}"'
-                                )
-                                sys.exit(1)
-                        elif " -t " in self.conf["ssh"]:
-                            # case scp upload is allowed
-                            if self.conf["scp_upload"]:
-                                if "scpforce" in self.conf:
-                                    cmdsplit = self.conf["ssh"].split(" ")
-                                    scppath = os.path.realpath(cmdsplit[-1])
-                                    forcedpath = os.path.realpath(self.conf["scpforce"])
-                                    if scppath != forcedpath:
-                                        self.log.error(
-                                            f"SCP: forced SCP directory: {scppath}"
-                                        )
-                                        cmdsplit.pop(-1)
-                                        cmdsplit.append(forcedpath)
-                                        self.conf["ssh"] = string.join(cmdsplit)
-                                self.log.error(f'SCP: PUT "{self.conf["ssh"]}"')
-                            # case scp upload is forbidden
-                            else:
-                                self.log.error(
-                                    f'SCP: upload forbidden: "{self.conf["ssh"]}"'
-                                )
-                                sys.exit(1)
-                        retcode = utils.cmd_parse_execute(self.conf["ssh"], cli)
-                        self.log.error("SCP disconnect")
-                        sys.exit(retcode)
-                    else:
-                        self.ssh_warn("SCP connection", self.conf["ssh"], "scp")
-
-                # check if command is in allowed overssh commands
-                elif self.conf["ssh"]:
-                    # replace aliases
-                    self.conf["ssh"] = utils.get_aliases(
-                        self.conf["ssh"], self.conf["aliases"]
-                    )
-                    # if command is not "secure", exit
-                    ret_check_secure, self.conf = sec.check_secure(
-                        self.conf["ssh"], self.conf, strict=1, ssh=1
-                    )
-                    if ret_check_secure:
-                        self.ssh_warn("char/command over SSH", self.conf["ssh"])
-                    # else
-                    self.log.error(f'Over SSH: "{self.conf["ssh"]}"')
-                    # if command is "help"
-                    if self.conf["ssh"] == "help":
-                        cli.do_help(None)
-                        retcode = 0
-                    else:
-                        retcode = utils.cmd_parse_execute(self.conf["ssh"], cli)
-                    self.log.error("Exited")
-                    sys.exit(retcode)
-
-                # else warn and log
-                else:
-                    self.ssh_warn("command over SSH", self.conf["ssh"])
-
-            else:
-                # case of shell escapes
-                self.ssh_warn("shell escape", self.conf["ssh"])
-
-    def ssh_warn(self, message, command="", key=""):
-        """log and warn if forbidden action over SSH"""
-        if key == "scp":
-            self.log.critical(f"*** forbidden {message}")
-            self.log.error(f"*** SCP command: {command}")
-        else:
-            self.log.critical(f'*** forbidden {message}: "{command}"')
-        self.stderr.write("This incident has been reported.\n")
-        self.log.error("Exited")
-        sys.exit(1)
-
     def set_noexec(self):
         """This method checks the existence of the sudo_noexec library."""
         # list of standard sudo_noexec.so file location
diff --git a/lshell/sec.py b/lshell/sec.py
index 9bbd14b..87ec056 100644
--- a/lshell/sec.py
+++ b/lshell/sec.py
@@ -1,26 +1,12 @@
-#
-#  Limited command Shell (lshell)
-#
-#  Copyright (C) 2008-2024 Ignace Mouzannar <ghantoos@ghantoos.org>
-#
-#  This file is part of lshell
-#
-#  This program is free software: you can redistribute it and/or modify
-#  it under the terms of the GNU General Public License as published by
-#  the Free Software Foundation, either version 3 of the License, or
-#  (at your option) any later version.
-#
-#  This program is distributed in the hope that it will be useful,
-#  but WITHOUT ANY WARRANTY; without even the implied warranty of
-#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-#  GNU General Public License for more details.
-#
-#  You should have received a copy of the GNU General Public License
-#  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+""" This module is used to check the security of the commands entered by the
+user. It checks if the command is allowed, if the path is allowed, if the
+command contains forbidden characters, etc.
+"""
 
 import sys
 import re
 import os
+import subprocess
 
 # import lshell specifics
 from lshell import utils
@@ -85,7 +71,6 @@ def check_path(line, conf, completion=None, ssh=None, strict=None):
         if re.findall(r"\$|\*|\?", item):
             # remove quotes if available
             item = re.sub("\"|'", "", item)
-            import subprocess
 
             p = subprocess.Popen(
                 f"`which echo` {item}",
@@ -252,7 +237,7 @@ def check_secure(line, conf, strict=None, ssh=None):
 
         # in case of a sudo command, check in sudo_commands list if allowed
         if command == "sudo":
-            if type(cmdargs) is list:
+            if isinstance(cmdargs, list):
                 # allow the -u (user) flag
                 if cmdargs[1] == "-u" and cmdargs:
                     sudocmd = cmdargs[3]
diff --git a/lshell/shellcmd.py b/lshell/shellcmd.py
index dcb238e..60e1095 100644
--- a/lshell/shellcmd.py
+++ b/lshell/shellcmd.py
@@ -1,22 +1,8 @@
-#
-#  Limited command Shell (lshell)
-#
-#  Copyright (C) 2008-2024 Ignace Mouzannar <ghantoos@ghantoos.org>
-#
-#  This file is part of lshell
-#
-#  This program is free software: you can redistribute it and/or modify
-#  it under the terms of the GNU General Public License as published by
-#  the Free Software Foundation, either version 3 of the License, or
-#  (at your option) any later version.
-#
-#  This program is distributed in the hope that it will be useful,
-#  but WITHOUT ANY WARRANTY; without even the implied warranty of
-#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-#  GNU General Public License for more details.
-#
-#  You should have received a copy of the GNU General Public License
-#  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+""" This module contains the main class of lshell, it is the class that is
+responsible for the command line interface. It inherits from the cmd.Cmd class
+from the Python standard library. It offers the default methods to add
+security checks, logging, etc.
+"""
 
 import cmd
 import sys
@@ -26,8 +12,9 @@
 import readline
 
 # import lshell specifics
+from lshell.checkconfig import CheckConfig
 from lshell import utils
-from lshell import builtins
+from lshell import builtincmd
 from lshell import sec
 
 
@@ -100,14 +87,14 @@ def __getattr__(self, attr):
 
         # in case the configuration file has been modified, reload it
         if self.conf["config_mtime"] != os.path.getmtime(self.conf["configfile"]):
-            from lshell.checkconfig import CheckConfig
-
             self.conf = CheckConfig(
                 ["--config", self.conf["configfile"]], refresh=1
             ).returnconf()
             self.conf["promptprint"] = utils.updateprompt(os.getcwd(), self.conf)
             self.log = self.conf["logpath"]
 
+        self.check_scp_sftp()
+
         if self.g_cmd in ["quit", "exit", "EOF"]:
             self.do_exit()
 
@@ -148,7 +135,7 @@ def __getattr__(self, attr):
                 p = re.compile(r"(\s|^)(\$\?)(\s|$)")
             self.g_line = p.sub(rf" {self.retcode} \3", self.g_line)
 
-            if type(self.conf["aliases"]) is dict:
+            if isinstance(self.conf["aliases"], dict):
                 self.g_line = utils.get_aliases(self.g_line, self.conf["aliases"])
 
             self.log.info(f'CMD: "{self.g_line}"')
@@ -164,7 +151,7 @@ def __getattr__(self, attr):
                     directory = directory.split("cd", 1)[1].strip()
                     # change directory then, if success, execute the rest of
                     # the cmd line
-                    self.retcode, self.conf = builtins.cd(directory, self.conf)
+                    self.retcode, self.conf = builtincmd.cd(directory, self.conf)
 
                     if self.retcode == 0:
                         cmd_split = re.split(r";|&&|&|\|\||\|", command)
@@ -173,27 +160,27 @@ def __getattr__(self, attr):
                 else:
                     # set directory to command line argument and change dir
                     directory = self.g_arg
-                    self.retcode, self.conf = builtins.cd(directory, self.conf)
+                    self.retcode, self.conf = builtincmd.cd(directory, self.conf)
 
             # built-in lpath function: list all allowed path
             elif self.g_cmd == "lpath":
-                self.retcode = builtins.lpath(self.conf)
+                self.retcode = builtincmd.lpath(self.conf)
             # built-in lsudo function: list all allowed sudo commands
             elif self.g_cmd == "lsudo":
-                self.retcode = builtins.lsudo(self.conf)
+                self.retcode = builtincmd.lsudo(self.conf)
             # built-in history function: print command history
             elif self.g_cmd == "history":
-                self.retcode = builtins.history(self.conf, self.log)
+                self.retcode = builtincmd.history(self.conf, self.log)
             # built-in export function
             elif self.g_cmd == "export":
-                self.retcode, var = builtins.export(self.g_line)
+                self.retcode, var = builtincmd.export(self.g_line)
                 if self.retcode == 1:
                     self.log.critical(f"** forbidden environment variable '{var}'")
             # case 'cd' is in an alias e.g. {'toto':'cd /var/tmp'}
             elif self.g_line[0:2] == "cd":
                 self.g_cmd = self.g_line.split()[0]
                 directory = " ".join(self.g_line.split()[1:])
-                self.retcode, self.conf = builtins.cd(directory, self.conf)
+                self.retcode, self.conf = builtincmd.cd(directory, self.conf)
 
             else:
                 self.retcode = utils.cmd_parse_execute(self.g_line, self)
@@ -206,6 +193,115 @@ def __getattr__(self, attr):
             self.mytimer(self.conf["timer"])
         return object.__getattribute__(self, attr)
 
+    def check_scp_sftp(self):
+        """This method checks if the user is trying to SCP a file onto the
+        server. If this is the case, it checks if the user is allowed to use
+        SCP or not, and    acts as requested. : )
+        """
+
+        if "ssh" in self.conf:
+            if "SSH_CLIENT" in os.environ and "SSH_TTY" not in os.environ:
+                # check if sftp is requested and allowed
+                if "sftp-server" in self.conf["ssh"]:
+                    if self.conf["sftp"] == 1:
+                        self.log.error("SFTP connect")
+                        retcode = utils.cmd_parse_execute(self.conf["ssh"])
+                        self.log.error("SFTP disconnect")
+                        sys.exit(retcode)
+                    else:
+                        self.log.error("*** forbidden SFTP connection")
+                        sys.exit(1)
+
+                # initialize cli session
+                cli = ShellCmd(self.conf, None, None, None, None, self.conf["ssh"])
+                ret_check_path, self.conf = sec.check_path(
+                    self.conf["ssh"], self.conf, ssh=1
+                )
+                if ret_check_path == 1:
+                    self.ssh_warn("path over SSH", self.conf["ssh"])
+
+                # check if scp is requested and allowed
+                if self.conf["ssh"].startswith("scp "):
+                    if self.conf["scp"] == 1 or "scp" in self.conf["overssh"]:
+                        if " -f " in self.conf["ssh"]:
+                            # case scp download is allowed
+                            if self.conf["scp_download"]:
+                                self.log.error(f'SCP: GET "{self.conf["ssh"]}"')
+                            # case scp download is forbidden
+                            else:
+                                self.log.error(
+                                    f'SCP: download forbidden: "{self.conf["ssh"]}"'
+                                )
+                                sys.exit(1)
+                        elif " -t " in self.conf["ssh"]:
+                            # case scp upload is allowed
+                            if self.conf["scp_upload"]:
+                                if "scpforce" in self.conf:
+                                    cmdsplit = self.conf["ssh"].split(" ")
+                                    scppath = os.path.realpath(cmdsplit[-1])
+                                    forcedpath = os.path.realpath(self.conf["scpforce"])
+                                    if scppath != forcedpath:
+                                        self.log.error(
+                                            f"SCP: forced SCP directory: {scppath}"
+                                        )
+                                        cmdsplit.pop(-1)
+                                        cmdsplit.append(forcedpath)
+                                        self.conf["ssh"] = " ".join(cmdsplit)
+                                self.log.error(f'SCP: PUT "{self.conf["ssh"]}"')
+                            # case scp upload is forbidden
+                            else:
+                                self.log.error(
+                                    f'SCP: upload forbidden: "{self.conf["ssh"]}"'
+                                )
+                                sys.exit(1)
+                        retcode = utils.cmd_parse_execute(self.conf["ssh"], cli)
+                        self.log.error("SCP disconnect")
+                        sys.exit(retcode)
+                    else:
+                        self.ssh_warn("SCP connection", self.conf["ssh"], "scp")
+
+                # check if command is in allowed overssh commands
+                elif self.conf["ssh"]:
+                    # replace aliases
+                    self.conf["ssh"] = utils.get_aliases(
+                        self.conf["ssh"], self.conf["aliases"]
+                    )
+                    # if command is not "secure", exit
+                    ret_check_secure, self.conf = sec.check_secure(
+                        self.conf["ssh"], self.conf, strict=1, ssh=1
+                    )
+                    if ret_check_secure:
+                        self.ssh_warn("char/command over SSH", self.conf["ssh"])
+                    # else
+                    self.log.error(f'Over SSH: "{self.conf["ssh"]}"')
+                    # if command is "help"
+                    if self.conf["ssh"] == "help":
+                        cli.do_help(None)
+                        retcode = 0
+                    else:
+                        retcode = utils.cmd_parse_execute(self.conf["ssh"], cli)
+                    self.log.error("Exited")
+                    sys.exit(retcode)
+
+                # else warn and log
+                else:
+                    self.ssh_warn("command over SSH", self.conf["ssh"])
+
+            else:
+                # case of shell escapes
+                self.ssh_warn("shell escape", self.conf["ssh"])
+
+    def ssh_warn(self, message, command="", key=""):
+        """log and warn if forbidden action over SSH"""
+        if key == "scp":
+            self.log.critical(f"*** forbidden {message}")
+            self.log.error(f"*** SCP command: {command}")
+        else:
+            self.log.critical(f'*** forbidden {message}: "{command}"')
+        sys.stderr.write("This incident has been reported.\n")
+        self.log.error("Exited")
+        sys.exit(1)
+
     def run_script_mode(self, script):
         """Process commands from a script."""
         with open(script, "r") as script_file:
@@ -268,7 +364,7 @@ def cmdloop(self, intro=None):
                         self.stdout.write(self.conf["promptprint"])
                         self.stdout.flush()
                         line = self.stdin.readline()
-                        if not len(line):
+                        if not line:
                             line = "EOF"
                         else:
                             # chop \n
@@ -315,7 +411,7 @@ def complete(self, text, state):
             ):
                 compfunc = self.completechdir
             elif begidx > 0:
-                cmd, args, foo = self.parseline(line)
+                cmd, args, _ = self.parseline(line)
                 if cmd == "":
                     compfunc = self.completedefault
                 else:
diff --git a/lshell/utils.py b/lshell/utils.py
index ab340e5..3848b40 100644
--- a/lshell/utils.py
+++ b/lshell/utils.py
@@ -1,38 +1,22 @@
-#
-#    Limited command Shell (lshell)
-#
-#  Copyright (C) 2008-2024 Ignace Mouzannar <ghantoos@ghantoos.org>
-#
-#  This file is part of lshell
-#
-#  This program is free software: you can redistribute it and/or modify
-#  it under the terms of the GNU General Public License as published by
-#  the Free Software Foundation, either version 3 of the License, or
-#  (at your option) any later version.
-#
-#  This program is distributed in the hope that it will be useful,
-#  but WITHOUT ANY WARRANTY; without even the implied warranty of
-#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-#  GNU General Public License for more details.
-#
-#  You should have received a copy of the GNU General Public License
-#  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+""" Utils for lshell """
 
 import re
 import subprocess
 import os
 import sys
+import random
+import string
 from getpass import getuser
 
 # import lshell specifics
 from lshell import variables
-from lshell import builtins
+from lshell import builtincmd
 
 
-def usage():
+def usage(exitcode=1):
     """Prints the usage"""
-    sys.stderr.write(variables.usage)
-    sys.exit(0)
+    sys.stderr.write(variables.USAGE)
+    sys.exit(exitcode)
 
 
 def version():
@@ -43,9 +27,6 @@ def version():
 
 def random_string(length):
     """generate a random string"""
-    import random
-    import string
-
     randstring = ""
     for char in range(length):
         char = random.choice(string.ascii_letters + string.digits)
@@ -90,8 +71,7 @@ def cmd_parse_execute(command_line, shell_context=None):
     # Split command line by shell grammar: '&&', '||', and ';;'
     cmd_split = re.split(r"(;;|&&|\|\|)", command_line)
 
-    # Initialize a variable to track whether the previous command succeeded or failed
-    previous_retcode = 0
+    retcode = 0  # Initialize return code
 
     # Iterate over commands and operators
     for i in range(0, len(cmd_split), 2):
@@ -99,9 +79,9 @@ def cmd_parse_execute(command_line, shell_context=None):
         operator = cmd_split[i - 1].strip() if i > 0 else None
 
         # Only execute commands based on the previous operator and return code
-        if operator == "&&" and previous_retcode != 0:
+        if operator == "&&" and retcode != 0:
             continue
-        elif operator == "||" and previous_retcode == 0:
+        elif operator == "||" and retcode == 0:
             continue
 
         # Get the executable command
@@ -117,17 +97,14 @@ def cmd_parse_execute(command_line, shell_context=None):
             elif executable == "exit":
                 shell_context.do_exit(command)
             elif executable == "history":
-                builtins.history(shell_context.conf, shell_context.log)
+                builtincmd.history(shell_context.conf, shell_context.log)
             elif executable == "cd":
-                retcode = builtins.cd(argument, shell_context.conf)
+                retcode = builtincmd.cd(argument, shell_context.conf)
             else:
-                retcode = getattr(builtins, executable)(shell_context.conf)
+                retcode = getattr(builtincmd, executable)(shell_context.conf)
         else:
             retcode = exec_cmd(command)
 
-        # Update the previous return code
-        previous_retcode = retcode
-
     return retcode
 
 
diff --git a/lshell/variables.py b/lshell/variables.py
index 804bb82..8645b42 100644
--- a/lshell/variables.py
+++ b/lshell/variables.py
@@ -1,22 +1,4 @@
-#
-#  Limited command Shell (lshell)
-#
-#  Copyright (C) 2008-2024 Ignace Mouzannar <ghantoos@ghantoos.org>
-#
-#  This file is part of lshell
-#
-#  This program is free software: you can redistribute it and/or modify
-#  it under the terms of the GNU General Public License as published by
-#  the Free Software Foundation, either version 3 of the License, or
-#  (at your option) any later version.
-#
-#  This program is distributed in the hope that it will be useful,
-#  but WITHOUT ANY WARRANTY; without even the implied warranty of
-#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-#  GNU General Public License for more details.
-#
-#  You should have received a copy of the GNU General Public License
-#  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+""" This file contains all the variables used in lshell """
 
 import sys
 import os
@@ -33,20 +15,20 @@
 lshell_path = os.path.abspath(__file__).split("/lib/")[0]
 if sys.exec_prefix != "/usr":
     # for *BSD
-    conf_prefix = sys.exec_prefix
+    CONF_PREFIX = sys.exec_prefix
 elif lshell_path == "/home/ghantoos/.local":
     # for *Linux user install
-    conf_prefix = lshell_path
+    CONF_PREFIX = lshell_path
 else:
     # for *Linux system-wide install
-    conf_prefix = ""
-configfile = conf_prefix + "/etc/lshell.conf"
+    CONF_PREFIX = ""
+configfile = CONF_PREFIX + "/etc/lshell.conf"
 
 # history file
-history_file = ".lhistory"
+HISTORY_FILE = ".lhistory"
 
 # help text
-usage = f"""Usage: lshell [OPTIONS]
+USAGE = f"""Usage: lshell [OPTIONS]
   --config <file>   : Config file location (default {configfile})
   --<param> <value> : where <param> is *any* config file parameter
   -h, --help        : Show this help message
@@ -54,8 +36,9 @@
 """
 
 # Intro Text
-intro = """You are in a limited shell.
+INTRO = """You are in a limited shell.
 Type '?' or 'help' to get the list of allowed commands"""
+
 # configuration parameters
 configparams = [
     "config=",
diff --git a/setup.py b/setup.py
index 348d4ef..2054660 100755
--- a/setup.py
+++ b/setup.py
@@ -1,27 +1,9 @@
-#
-#  Limited command Shell (lshell)
-#
-#  Copyright (C) 2008-2024 Ignace Mouzannar <ghantoos@ghantoos.org>
-#
-#  This file is part of lshell
-#
-#  This program is free software: you can redistribute it and/or modify
-#  it under the terms of the GNU General Public License as published by
-#  the Free Software Foundation, either version 3 of the License, or
-#  (at your option) any later version.
-#
-#  This program is distributed in the hope that it will be useful,
-#  but WITHOUT ANY WARRANTY; without even the implied warranty of
-#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-#  GNU General Public License for more details.
-#
-#  You should have received a copy of the GNU General Public License
-#  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+""" Setup script for lshell """
 
-from setuptools import setup, find_packages
 import os
-from setuptools.command.install import install
 import shutil
+from setuptools import setup, find_packages
+from setuptools.command.install import install
 
 # import lshell specifics
 from lshell.variables import __version__
diff --git a/test/__init__.py b/test/__init__.py
index a5a1bac..00dc735 100644
--- a/test/__init__.py
+++ b/test/__init__.py
@@ -1,3 +1,5 @@
+""" This module is used to run all the tests in the test directory. """
+
 from test import test_functional, test_unit
 
 if __name__ == "__main__":
diff --git a/test/test_functional.py b/test/test_functional.py
index 5c0fd32..5ea7253 100644
--- a/test/test_functional.py
+++ b/test/test_functional.py
@@ -1,10 +1,12 @@
-import unittest
-import pexpect
+"""Functional tests for lshell"""
+
 import os
+import unittest
 import subprocess
 from getpass import getuser
 import tempfile
 import shutil
+import pexpect
 
 # import lshell specifics
 from lshell import utils
@@ -13,6 +15,7 @@
 
 
 class TestFunctions(unittest.TestCase):
+    """Functional tests for lshell"""
 
     user = getuser()
 
@@ -43,7 +46,7 @@ def test_02_builtin_ls_command(self):
         cout = p.stdout
         expected = cout.read(-1)
         self.child.sendline("ls")
-        self.child.expect("%s:~\\$" % self.user)
+        self.child.expect(f"{self.user}:~\\$")
         output = self.child.before.decode("utf8").split("ls\r", 1)[1]
         self.assertEqual(len(expected.strip().split()), len(output.strip().split()))
 
@@ -361,7 +364,7 @@ def test_24_cd_and_command(self):
         result = self.child.before.decode("utf8").split("\n")[1].strip()
         self.assertEqual(expected, result)
 
-    def test_25_KeyboardInterrupt(self):
+    def test_25_keyboard_interrupt(self):
         """F25 | test cat(1) with KeyboardInterrupt, should not exit"""
         self.child = pexpect.spawn(
             f"{TOPDIR}/bin/lshell "
@@ -381,6 +384,8 @@ def test_25_KeyboardInterrupt(self):
                 expected = "foo"
             elif result.startswith("^C"):
                 expected = "^C"
+            else:
+                expected = "unknown"
         except IndexError:
             # outputs u' ^C' on Debian
             expected = "^C"
@@ -490,7 +495,10 @@ def test_31_security_echo_freedom_and_help(self):
         self.assertEqual(expected_help_output, help_output)
 
         # Step 2: Enter `echo FREEDOM! && help () sh && help`
-        expected_output = "FREEDOM!\r\ncd  clear  echo  exit  help  history  ll  lpath  ls  lsudo\r\ncd  clear  echo  exit  help  history  ll  lpath  ls  lsudo"
+        expected_output = (
+            "FREEDOM!\r\ncd  clear  echo  exit  help  history  ll  lpath  ls  lsudo\r\n"
+            "cd  clear  echo  exit  help  history  ll  lpath  ls  lsudo"
+        )
         self.child.sendline("echo FREEDOM! && help () sh && help")
         self.child.expect(f"{self.user}:~\\$")
 
@@ -588,14 +596,19 @@ def test_36_env_vars_file_not_found(self):
 
         # Inject the environment variable file path
         self.child = pexpect.spawn(
-            f"{TOPDIR}/bin/lshell --config {TOPDIR}/etc/lshell.conf --env_vars_files \"['{missing_file_path}']\""
+            f"{TOPDIR}/bin/lshell --config {TOPDIR}/etc/lshell.conf "
+            f"--env_vars_files \"['{missing_file_path}']\""
         )
 
         # Expect the prompt after shell startup
         self.child.expect(f"{self.user}:~\\$")
 
         # Simulate what happens when the environment variable file is missing
-        expected = f"ERROR: Unable to read environment file: {missing_file_path}\r\nYou are in a limited shell.\r\nType '?' or 'help' to get the list of allowed commands\r\n"
+        expected = (
+            f"ERROR: Unable to read environment file: {missing_file_path}\r\n"
+            "You are in a limited shell.\r\n"
+            "Type '?' or 'help' to get the list of allowed commands\r\n"
+        )
 
         # Check the error message in the output
         self.assertIn(expected, self.child.before.decode("utf8"))
@@ -613,7 +626,8 @@ def test_37_load_env_vars_from_file(self):
 
         # Set the temp env file path in the config
         self.child = pexpect.spawn(
-            f"{TOPDIR}/bin/lshell --config {TOPDIR}/etc/lshell.conf --env_vars_files \"['{temp_env_file_path}']\""
+            f"{TOPDIR}/bin/lshell --config {TOPDIR}/etc/lshell.conf "
+            f"--env_vars_files \"['{temp_env_file_path}']\""
         )
         self.child.expect(f"{self.user}:~\\$")
 
@@ -668,9 +682,6 @@ def test_38_script_execution_with_template(self):
 cd  clear  echo  exit  help  history  ll  lpath  ls  lsudo\r
 *** forbidden path: /"""
 
-        # Set maxDiff to None to see the full diff
-        self.maxDiff = None
-
         # Wait for the script to finish executing
         self.child.expect(pexpect.EOF)
 
@@ -727,9 +738,6 @@ def test_39_script_execution_with_template_strict(self):
 *** forbidden path -> "/"\r
 *** Kicked out"""
 
-        # Step 4: Set maxDiff to None to see the full diff
-        self.maxDiff = None
-
         # Wait for the script to finish executing
         self.child.expect(pexpect.EOF)
 
diff --git a/test/test_unit.py b/test/test_unit.py
index c38b8c7..e3c1611 100644
--- a/test/test_unit.py
+++ b/test/test_unit.py
@@ -1,5 +1,7 @@
-import unittest
+""" Unit tests for lshell """
+
 import os
+import unittest
 from getpass import getuser
 
 # import lshell specifics
@@ -7,70 +9,73 @@
 from lshell.checkconfig import CheckConfig
 from lshell.utils import get_aliases, updateprompt
 from lshell.variables import builtins_list
-from lshell import builtins
+from lshell import builtincmd
 from lshell import sec
 
 TOPDIR = f"{os.path.dirname(os.path.realpath(__file__))}/../"
 
 
 class TestFunctions(unittest.TestCase):
+    """Unit tests for lshell"""
+
     args = [f"--config={TOPDIR}/etc/lshell.conf", "--quiet=1"]
     userconf = CheckConfig(args).returnconf()
-    shell = ShellCmd(userconf, args)
 
     def test_03_checksecure_doublepipe(self):
         """U03 | double pipes should be allowed, even if pipe is forbidden"""
         args = self.args + ["--forbidden=['|']"]
         userconf = CheckConfig(args).returnconf()
-        INPUT = "ls || ls"
-        return self.assertEqual(sec.check_secure(INPUT, userconf)[0], 0)
+        input_command = "ls || ls"
+        return self.assertEqual(sec.check_secure(input_command, userconf)[0], 0)
 
     def test_04_checksecure_forbiddenpipe(self):
         """U04 | forbid pipe, should return 1"""
         args = self.args + ["--forbidden=['|']"]
         userconf = CheckConfig(args).returnconf()
-        INPUT = "ls | ls"
-        return self.assertEqual(sec.check_secure(INPUT, userconf)[0], 1)
+        input_command = "ls | ls"
+        return self.assertEqual(sec.check_secure(input_command, userconf)[0], 1)
 
     def test_05_checksecure_forbiddenchar(self):
         """U05 | forbid character, should return 1"""
         args = self.args + ["--forbidden=['l']"]
         userconf = CheckConfig(args).returnconf()
-        INPUT = "ls"
-        return self.assertEqual(sec.check_secure(INPUT, userconf)[0], 1)
+        input_command = "ls"
+        return self.assertEqual(sec.check_secure(input_command, userconf)[0], 1)
 
     def test_06_checksecure_sudo_command(self):
         """U06 | quoted text should not be forbidden"""
-        INPUT = "sudo ls"
-        return self.assertEqual(sec.check_secure(INPUT, self.userconf)[0], 1)
+        input_command = "sudo ls"
+        return self.assertEqual(sec.check_secure(input_command, self.userconf)[0], 1)
 
     def test_07_checksecure_notallowed_command(self):
         """U07 | forbidden command, should return 1"""
         args = self.args + ["--allowed=['ls']"]
         userconf = CheckConfig(args).returnconf()
-        INPUT = "ll"
-        return self.assertEqual(sec.check_secure(INPUT, userconf)[0], 1)
+        input_command = "ll"
+        return self.assertEqual(sec.check_secure(input_command, userconf)[0], 1)
 
     def test_08_checkpath_notallowed_path(self):
         """U08 | forbidden command, should return 1"""
         args = self.args + ["--path=['/home', '/var']"]
         userconf = CheckConfig(args).returnconf()
-        INPUT = "cd /tmp"
-        return self.assertEqual(sec.check_path(INPUT, userconf)[0], 1)
+        input_command = "cd /tmp"
+        return self.assertEqual(sec.check_path(input_command, userconf)[0], 1)
 
     def test_09_checkpath_notallowed_path_completion(self):
         """U09 | forbidden command, should return 1"""
         args = self.args + ["--path=['/home', '/var']"]
         userconf = CheckConfig(args).returnconf()
-        INPUT = "cd /tmp/"
-        return self.assertEqual(sec.check_path(INPUT, userconf, completion=1)[0], 1)
+        input_command = "cd /tmp/"
+        return self.assertEqual(
+            sec.check_path(input_command, userconf, completion=1)[0], 1
+        )
 
     def test_10_checkpath_dollarparenthesis(self):
         """U10 | when $() is allowed, return 0 if path allowed"""
         args = self.args + ["--forbidden=[';', '&', '|','`','>','<', '${']"]
         userconf = CheckConfig(args).returnconf()
-        INPUT = "echo $(echo aze)"
-        return self.assertEqual(sec.check_path(INPUT, userconf)[0], 0)
+        input_command = "echo $(echo aze)"
+        return self.assertEqual(sec.check_path(input_command, userconf)[0], 0)
 
     def test_11_checkconfig_configoverwrite(self):
         """U12 | forbid ';', then check_secure should return 1"""
@@ -81,20 +86,22 @@ def test_11_checkconfig_configoverwrite(self):
     def test_12_overssh(self):
         """U12 | command over ssh"""
         args = self.args + ["--overssh=['exit']", "-c exit"]
+        userconf = CheckConfig(args).returnconf()
+        shell = ShellCmd(userconf, args)
         os.environ["SSH_CLIENT"] = "8.8.8.8 36000 22"
         if "SSH_TTY" in os.environ:
             os.environ.pop("SSH_TTY")
         with self.assertRaises(SystemExit) as cm:
-            CheckConfig(args).returnconf()
+            shell.check_scp_sftp()
         return self.assertEqual(cm.exception.code, 0)
 
     def test_13_multiple_aliases_with_separator(self):
         """U13 | multiple aliases using &&, || and ; separators"""
         # enable &, | and ; characters
         aliases = {"foo": "foo -l", "bar": "open"}
-        INPUT = "foo; fooo  ;bar&&foo  &&   foo | bar||bar   ||     foo"
+        input_command = "foo; fooo  ;bar&&foo  &&   foo | bar||bar   ||     foo"
         return self.assertEqual(
-            get_aliases(INPUT, aliases),
+            get_aliases(input_command, aliases),
             " foo -l; fooo  ; open&& foo -l  " "&& foo -l | open|| open   || foo -l",
         )
 
@@ -138,16 +145,16 @@ def test_17_allowed_exec_cmd(self):
 
     def test_18_forbidden_environment(self):
         """U18 | unsafe environment are forbidden"""
-        INPUT = "export LD_PRELOAD=/lib64/ld-2.21.so"
-        args = INPUT
-        retcode = builtins.export(args)[0]
+        input_command = "export LD_PRELOAD=/lib64/ld-2.21.so"
+        args = input_command
+        retcode = builtincmd.export(args)[0]
         return self.assertEqual(retcode, 1)
 
     def test_19_allowed_environment(self):
         """U19 | other environment are accepted"""
-        INPUT = "export MY_PROJECT_VERSION=43"
-        args = INPUT
-        retcode = builtins.export(args)[0]
+        input_command = "export MY_PROJECT_VERSION=43"
+        args = input_command
+        retcode = builtincmd.export(args)[0]
         return self.assertEqual(retcode, 0)
 
     def test_20_winscp_allowed_commands(self):
@@ -210,15 +217,15 @@ def test_25_disable_ld_preload(self):
 
     def test_26_checksecure_quoted_command(self):
         """U26 | quoted command should be parsed"""
-        INPUT = 'echo 1 && "bash"'
-        return self.assertEqual(sec.check_secure(INPUT, self.userconf)[0], 1)
+        input_command = 'echo 1 && "bash"'
+        return self.assertEqual(sec.check_secure(input_command, self.userconf)[0], 1)
 
     def test_27_checksecure_quoted_command(self):
         """U27 | quoted command should be parsed"""
-        INPUT = '"bash" && echo 1'
-        return self.assertEqual(sec.check_secure(INPUT, self.userconf)[0], 1)
+        input_command = '"bash" && echo 1'
+        return self.assertEqual(sec.check_secure(input_command, self.userconf)[0], 1)
 
     def test_28_checksecure_quoted_command(self):
         """U28 | quoted command should be parsed"""
-        INPUT = "echo'/1.sh'"
-        return self.assertEqual(sec.check_secure(INPUT, self.userconf)[0], 1)
+        input_command = "echo'/1.sh'"
+        return self.assertEqual(sec.check_secure(input_command, self.userconf)[0], 1)