update: Chapter2 UNIX 标准及实现

Chapter-01/README.md

@@ -110,7 +110,7 @@ pid: 90612
 % ^Cinterrupt
 ^C% interrupt
 [另开一个控制台]
-kill 90612
+$ kill 90612
 [刚刚的程序]
 % Terminated: 15
 ```

Chapter-02/2.5.1.c

@@ -0,0 +1,24 @@
+#include <stdio.h>
+#include <limits.h>
+
+int main() {
+    printf("CHAR_BIT: %d\n", CHAR_BIT);
+    printf("CHAR_MAX: %d\n", CHAR_MAX);
+    printf("CHAR_MIN: %d\n", CHAR_MIN);
+    printf("SCHAR_MAX: %d\n", SCHAR_MAX);
+    printf("SCHAR_MIN: %d\n", SCHAR_MIN);
+    printf("INT_MAX: %d\n", INT_MAX);
+    printf("INT_MIN: %d\n", INT_MIN);
+    printf("UINT_MAX: %d\n", UINT_MAX);
+    printf("SHRT_MAX: %d\n", SHRT_MAX);
+    printf("SHRT_MIN: %d\n", SHRT_MIN);
+    printf("USHRT_MAX: %d\n", USHRT_MAX);
+    printf("LONG_MAX: %ld\n", LONG_MAX);
+    printf("LONG_MIN: %ld\n", LONG_MIN);
+    printf("ULONG_MAX: %lu\n", ULONG_MAX);
+    printf("LLONG_MAX: %lld\n", LLONG_MAX);
+    printf("LLONG_MIN: %lld\n", LLONG_MIN);
+    printf("ULLONG_MAX: %llu\n", ULLONG_MAX);
+    printf("MB_LEN_MAX: %d\n", MB_LEN_MAX);
+    return 0;
+}

Chapter-02/2.5.4.awk

@@ -0,0 +1,88 @@
+#!/usr/bin/awk -f
+BEGIN	{
+	printf("#include \"apue.h\"\n")
+	printf("#include <errno.h>\n")
+	printf("#include <limits.h>\n")
+	printf("\n")
+	printf("static void	pr_sysconf(char *, int);\n")
+	printf("static void	pr_pathconf(char *, char *, int);\n")
+	printf("\n")
+	printf("int\n")
+	printf("main(int argc, char *argv[])\n")
+	printf("{\n")
+	printf("\tif (argc != 2)\n")
+	printf("\t\terr_quit(\"usage: a.out <dirname>\");\n\n")
+	FS="\t+"
+	while (getline <"sysconf.sym" > 0) {
+		printf("#ifdef %s\n", $1)
+		printf("\tprintf(\"%s defined to be %%ld\\n\", (long)%s+0);\n",
+			 $1, $1)
+		printf("#else\n")
+		printf("\tprintf(\"no symbol for %s\\n\");\n", $1)
+		printf("#endif\n")
+		printf("#ifdef %s\n", $2)
+		printf("\tpr_sysconf(\"%s =\", %s);\n", $1, $2)
+		printf("#else\n")
+		printf("\tprintf(\"no symbol for %s\\n\");\n", $2)
+		printf("#endif\n")
+	}
+	close("sysconf.sym")
+	while (getline <"pathconf.sym" > 0) {
+		printf("#ifdef %s\n", $1)
+		printf("\tprintf(\"%s defined to be %%ld\\n\", (long)%s+0);\n",
+			$1, $1)
+		printf("#else\n")
+		printf("\tprintf(\"no symbol for %s\\n\");\n", $1)
+		printf("#endif\n")
+		printf("#ifdef %s\n", $2)
+		printf("\tpr_pathconf(\"%s =\", argv[1], %s);\n", $1, $2)
+		printf("#else\n")
+		printf("\tprintf(\"no symbol for %s\\n\");\n", $2)
+		printf("#endif\n")
+	}
+	close("pathconf.sym")
+	exit
+}
+END	{
+	printf("\texit(0);\n")
+	printf("}\n\n")
+	printf("static void\n")
+	printf("pr_sysconf(char *mesg, int name)\n")
+	printf("{\n")
+	printf("\tlong	val;\n\n")
+	printf("\tfputs(mesg, stdout);\n")
+	printf("\terrno = 0;\n")
+	printf("\tif ((val = sysconf(name)) < 0) {\n")
+	printf("\t\tif (errno != 0) {\n")
+	printf("\t\t\tif (errno == EINVAL)\n")
+	printf("\t\t\t\tfputs(\" (not supported)\\n\", stdout);\n")
+	printf("\t\t\telse\n")
+	printf("\t\t\t\terr_sys(\"sysconf error\");\n")
+	printf("\t\t} else {\n")
+	printf("\t\t\tfputs(\" (no limit)\\n\", stdout);\n")
+	printf("\t\t}\n")
+	printf("\t} else {\n")
+	printf("\t\tprintf(\" %%ld\\n\", val);\n")
+	printf("\t}\n")
+	printf("}\n\n")
+	printf("static void\n")
+	printf("pr_pathconf(char *mesg, char *path, int name)\n")
+	printf("{\n")
+	printf("\tlong	val;\n")
+	printf("\n")
+	printf("\tfputs(mesg, stdout);\n")
+	printf("\terrno = 0;\n")
+	printf("\tif ((val = pathconf(path, name)) < 0) {\n")
+	printf("\t\tif (errno != 0) {\n")
+	printf("\t\t\tif (errno == EINVAL)\n")
+	printf("\t\t\t\tfputs(\" (not supported)\\n\", stdout);\n")
+	printf("\t\t\telse\n")
+	printf("\t\t\t\terr_sys(\"pathconf error, path = %%s\", path);\n")
+	printf("\t\t} else {\n")
+	printf("\t\t\tfputs(\" (no limit)\\n\", stdout);\n")
+	printf("\t\t}\n")
+	printf("\t} else {\n")
+	printf("\t\tprintf(\" %%ld\\n\", val);\n")
+	printf("\t}\n")
+	printf("}\n")
+}

Chapter-02/2.5.4.c

@@ -0,0 +1 @@
+#include

Chapter-02/2.5.5.1.c

@@ -0,0 +1,50 @@
+#include "apue.h"
+#include <errno.h>
+#include <limits.h>
+
+#ifdef PATH_MAX
+static long pathmax = PATH_MAX;
+#else
+static long pathmax = 0;
+#endif
+
+static long posix_version = 0;
+static long xsi_version = 0;
+
+#define PATH_MAX_GUESS 1024
+
+char *path_alloc(size_t *sizep) {
+    char *ptr;
+    size_t size;
+
+    if (posix_version == 0)
+        posix_version = sysconf(_SC_VERSION);
+
+    if (xsi_version == 0)
+        xsi_version = sysconf(_SC_XOPEN_VERSION);
+
+    if (pathmax == 0) {
+        errno = 0;
+        if ((pathmax = pathconf("/", _PC_PATH_MAX)) < 0) {
+            if (errno == 0)
+                pathmax = PATH_MAX_GUESS;
+            else
+                err_sys("pathconf error for _PC_PATH_MAX");
+        } else {
+            pathmax++;
+        }
+    }
+
+    if ((posix_version < 200112L) && (xsi_version < 4))
+        size = pathmax + 1;
+    else
+        size = pathmax;
+
+    if ((ptr = malloc(size)) == NULL)
+        err_sys("malloc error for pathname");
+
+    if (sizep != NULL)
+        *sizep = size;
+
+    return (ptr);
+}

Chapter-02/2.5.5.2.c

@@ -0,0 +1,29 @@
+#include "apue.h"
+#include <errno.h>
+#include <limits.h>
+
+#ifdef OPEN_MAX
+static long openmax = OPEN_MAX;
+#else
+static long openmax = 0;
+#endif
+
+#define OPEN_MAX_GUESS 256
+
+long open_max() {
+    if (openmax == 0) {
+        errno = 0;
+        if ((openmax = sysconf(_SC_OPEN_MAX)) < 0) {
+            if (errno == 0)
+                openmax = OPEN_MAX_GUESS;
+            else
+                err_sys("sysconf error for _SC_OPEN_MAX");
+        }
+    }
+    return (openmax);
+}
+
+int main() {
+    printf("%ld\n", open_max());
+    return 0;
+}

Chapter-02/README.md

@@ -0,0 +1,105 @@
+## UNIX 标准及实现
+
+
+### 随书代码
+
+
+#### 2.5.1.c
+
+```<limits.h>``` 中定义的整型值大小
+
+```shell
+$ gcc 2.5.1.c
+$ ./a.out
+CHAR_BIT: 8
+CHAR_MAX: 127
+CHAR_MIN: -128
+SCHAR_MAX: 127
+SCHAR_MIN: -128
+INT_MAX: 2147483647
+INT_MIN: -2147483648
+UINT_MAX: -1
+SHRT_MAX: 32767
+SHRT_MIN: -32768
+USHRT_MAX: 65535
+LONG_MAX: 9223372036854775807
+LONG_MIN: -9223372036854775808
+ULONG_MAX: 18446744073709551615
+LLONG_MAX: 9223372036854775807
+LLONG_MIN: -9223372036854775808
+ULLONG_MAX: 18446744073709551615
+MB_LEN_MAX: 6
+```
+
+
+#### 2.5.4.awk && 2.5.4.c
+
+```shell
+$ awk -f 2.5.4.awk > conf.c
+$ gcc conf.c -lapue
+```
+
+[conf.c](conf.c)
+
+
+#### 2.5.5.2.c
+
+```shell
+$ gcc 2.5.5.2.c -lapue
+$ ./a.out
+10240
+```
+
+
+### 习题
+
+
+#### 在 2.8 节中提到一些基本系统数据类型可以在多个头文件中定义。例如，在 FreeBSD 8.0 中，size_t 在29 个不同的头文件中都有定义。由于一个程序可能包含这 29 个不同的头文件，但是 ISO C 却不允许对同一个名字进行多次 typedef ，那么如何编写这些头文件呢？
+
+使用宏定义保护。
+
+```
+#ifndef _MACHINE_TYPES_H_
+#define _MACHINE_TYPES_H_
+
+typedef int _int32_t;
+typedef unsigned int _uint32_t;
+
+.........
+
+typedef _uint32_t _size_t;
+
+.........
+
+#enddef
+```
+
+
+#### 检查系统的头文件，列出实现基本系统数据类型所用到的实际数据类型
+
+待续
+
+
+#### 改写图2-17中的程序，使其在 ```sysconf``` 为 ```OPEN_MAX``` 限制返回 ```LONG_MAX``` 时，避免进行不必要的处理
+
+在 ```sysconf``` 没有能够准确获得 ```OPEN_MAX``` 限制的时候，可以使用 ```getrlimit``` 来获得。
+
+```C
+long open_max()
+{
+    struct rlimit rl;
+    if (openmax == 0){
+        errno = 0;
+
+    if ((openmax = sysconf(_SC_OPEN_MAX)) < 0 || openmax == LONG_MAX) {
+            if ((openmax = getrlimit(RLIMIT_NOFILE, &rl)) < 0) {
+                err_sys("can not get file limit\n");
+            } else if (openmax == RLIM_INFINITY)
+                openmax = OPEN_MAX_GUESS;
+            else
+                openmax = rl.rlim_max;
+        }
+    }
+    return(openmax);
+}
+```

README.md

@@ -3,3 +3,4 @@
 ## 目录
 * [环境配置](apue.3e/)
 * [Chapter 1: UNIX 基础知识](Chapter-01/)
+* [UNIX 标准及实现](Chapter-02/)