apue.3第二章2-13 运行awk脚本输出到.c文件

╰半夏微凉° 2022-01-21 09:33 69阅读 0赞

在当前目录新建一个`1.awk`。

#!/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 %%d\\n\", %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 %%d\\n\", %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")
    }

根据awk文件的命令，再新建两个文件`sysconf.sym`和`pathconf.sym`，内容分别是：  
`ARG_MAX _SC_ARG_MAX`和`NAME_MAX _PC_NAME_MAX`。一定注意中间不是空格是tab，tab应该是awk命令的默认分隔符。  
然后运行`awk -f 1.awk > 1.c`：

*  `-f 1.awk`表示从这个脚本中读取awk命令以执行
 *  `> 1.c`表示所有的输出都重定向到`1.c`中
 *  不需要重定向输入，因为命令是自己读取当前目录中的`sysconf.sym`和`pathconf.sym`的。（跟命令的写法有关，因为这里是写死的，你也可以写成某个变量，然后在命令参数指定好这个输入文件）

运行后生成`1.c`文件：

#include "apue.h"
    #include <errno.h>
    #include <limits.h>
    
    static void	pr_sysconf(char *, int);
    static void	pr_pathconf(char *, char *, int);
    
    int
    main(int argc, char *argv[])
    { 
    	if (argc != 2)
    		err_quit("usage: a.out <dirname>");
    
    #ifdef ARG_MAX
    	printf("ARG_MAX defined to be %d\n", ARG_MAX+0);
    #else
    	printf("no symbol for ARG_MAX\n");
    #endif
    #ifdef _SC_ARG_MAX
    	pr_sysconf("ARG_MAX =", _SC_ARG_MAX);
    #else
    	printf("no symbol for _SC_ARG_MAX\n");
    #endif
    #ifdef NAME_MAX
    	printf("NAME_MAX defined to be %d\n", NAME_MAX+0);
    #else
    	printf("no symbol for NAME_MAX\n");
    #endif
    #ifdef _PC_NAME_MAX
    	pr_pathconf("NAME_MAX =", argv[1], _PC_NAME_MAX);
    #else
    	printf("no symbol for _PC_NAME_MAX\n");
    #endif
    	exit(0);
    }
    
    static void
    pr_sysconf(char *mesg, int name)
    { 
    	long	val;
    
    	fputs(mesg, stdout);
    	errno = 0;
    	if ((val = sysconf(name)) < 0) { 
    		if (errno != 0) { 
    			if (errno == EINVAL)
    				fputs(" (not supported)\n", stdout);
    			else
    				err_sys("sysconf error");
    		} else { 
    			fputs(" (no limit)\n", stdout);
    		}
    	} else { 
    		printf(" %ld\n", val);
    	}
    }
    
    static void
    pr_pathconf(char *mesg, char *path, int name)
    { 
    	long	val;
    
    	fputs(mesg, stdout);
    	errno = 0;
    	if ((val = pathconf(path, name)) < 0) { 
    		if (errno != 0) { 
    			if (errno == EINVAL)
    				fputs(" (not supported)\n", stdout);
    			else
    				err_sys("pathconf error, path = %s", path);
    		} else { 
    			fputs(" (no limit)\n", stdout);
    		}
    	} else { 
    		printf(" %ld\n", val);
    	}
    }

再运行`gcc 1.c -o 1 -l apue`生成可执行文件。  
然后就可以进行各种测试了：

*  `./1 .`测当前目录
 *  `./1 1.c`

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