diff --git a/self_hosted/runs_wrong.txt b/self_hosted/runs_wrong.txt
index 61286578..b44b692f 100644
--- a/self_hosted/runs_wrong.txt
+++ b/self_hosted/runs_wrong.txt
@@ -42,3 +42,4 @@ tests/syntax_error/bad_addressof.jou
 tests/wrong_type/assert.jou
 tests/wrong_type/cannot_be_indexed.jou
 tests/wrong_type/index.jou
+stdlib/ascii.jou
diff --git a/stdlib/ascii.jou b/stdlib/ascii.jou
new file mode 100644
index 00000000..5dedfca1
--- /dev/null
+++ b/stdlib/ascii.jou
@@ -0,0 +1,40 @@
+import "stdlib/str.jou"
+import "stdlib/mem.jou"
+
+# Test if a string is ASCII only.
+# TODO: test
+def is_ascii(s: byte*) -> bool:
+    for p = s; *p != '\0'; p++:
+        if *p >= 128:
+            return False
+    return True
+
+# Check for '0', '1', ..., '9'.
+# TODO: test
+def is_ascii_digit(b: byte) -> bool:
+    return '0' <= b and b <= '9'
+
+# Checks if the given byte is an ASCII punctuation character, such as '*' or '_' or '"'.
+# TODO: test
+def is_ascii_punctuation(b: byte) -> bool:
+    return strchr("!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~", b) != NULL
+
+# Checks if the given byte is an ASCII whitespace character, such as ' ' or '\n'.
+# TODO: test
+def is_ascii_whitespace(b: byte) -> bool:
+    return strchr("\t\n\x0b\x0c\r\x1c\x1d\x1e\x1f ", b) != NULL
+
+# Removes ASCII whitespace from both ends of a string in-place.
+# Similar to .strip() in Python or .trim() in JavaScript.
+def trim_ascii_whitespace(s: byte*) -> void:
+    start = s
+    while *start != '\0' and is_ascii_whitespace(*start):
+        start++
+
+    len = strlen(start)
+    while len > 0 and is_ascii_whitespace(start[len-1]):
+        len--
+
+    if start != s:
+        memcpy(s, start, len)
+    s[len] = '\0'
diff --git a/stdlib/io.jou b/stdlib/io.jou
index e46fb907..53f35083 100644
--- a/stdlib/io.jou
+++ b/stdlib/io.jou
@@ -60,6 +60,10 @@ declare fprintf(file: FILE *, pattern: byte*, ...) -> int
 declare fgetc(file: FILE*) -> int  # see getchar()
 declare fscanf(file: FILE*, pattern: byte*, ...) -> int
 
+# Reads at most n items of data, each of size "itemsize". Returns number of items read.
+# Usually this is used with itemsize 1, so return value is number of bytes.
+declare fread(destination: byte*, itemsize: long, n: long, file: FILE*) -> long
+
 # Ensure that output is actually written. It may remain buffered
 # if this function isn't called.
 declare fflush(file: FILE*) -> int
diff --git a/stdlib/str.jou b/stdlib/str.jou
index 90970591..17cd3a22 100644
--- a/stdlib/str.jou
+++ b/stdlib/str.jou
@@ -36,8 +36,13 @@ def ends_with(s: byte*, suffix: byte*) -> bool:
     return offset >= 0 and strcmp(&s[offset], suffix) == 0
 
 # Return how many bytes at start of s appear in the accept string.
+# For example, you can use strspn(s, " \t") to get the amount of indentation.
 declare strspn(s: byte*, accept: byte*) -> long
 
+# Return how many bytes at start of s do not appear in the reject string.
+# For example, you can use strcspn(s, "\n") to get the length of the first line.
+declare strcspn(s: byte*, accept: byte*) -> long
+
 # Copy a string. Assumes it fits. Returned value is dest.
 declare strcpy(dest: byte*, source: byte*) -> byte*
 
@@ -47,3 +52,8 @@ declare strcat(dest: byte*, source: byte*) -> byte*
 
 # Return a newly allocated (as in malloc()) copy of the string.
 declare strdup(s: byte*) -> byte*
+
+# Convert a string to an int.
+# Returns 0 on error, and ignores junk at end: atoi("123foo") == 123
+declare atoi(s: byte*) -> int
+declare atoll(s: byte*) -> long