![\"\"](\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250426053026-680c6f7275656.png\")
<\/p>\n\u76ee\u5f55<\/p>\n
\u4e00\u3001\u8fdb\u7a0b\u7a0b\u5e8f\u66ff\u6362<\/p>\n
1\u3001\u66ff\u6362\u539f\u7406<\/p>\n
2\u3001\u66ff\u6362\u51fd\u6570<\/p>\n
（1）\u51fd\u6570\u89e3\u91ca<\/p>\n
\u00a0 \u2460 filename \/ pathname<\/p>\n
\u00a0\u2461 \u53c2\u6570\u8868\u4f20\u9012<\/p>\n
\u00a0\u2462 \u73af\u5883\u53d8\u91cf\u8868\u4f20\u9012<\/p>\n
（2）\u547d\u540d\u7406\u89e3<\/p>\n
\u00a0\u4e8c\u3001\u81ea\u5b9a\u4e49shell\u547d\u4ee4\u884c\u89e3\u91ca\u5668<\/p>\n
1\u3001\u5b9e\u73b0\u539f\u7406<\/p>\n
2\u3001\u5b9e\u73b0\u4ee3\u7801<\/p>\n
（1）\u83b7\u53d6\u73af\u5883\u53d8\u91cf<\/p>\n
（2）\u8f93\u51fa\u547d\u4ee4\u884c\u63d0\u793a\u7b26<\/p>\n
（3）\u83b7\u53d6\u7528\u6237\u8f93\u5165\u7684\u547d\u4ee4<\/p>\n
（4）\u547d\u4ee4\u884c\u5206\u6790<\/p>\n
（5）\u68c0\u6d4b\u5e76\u6267\u884c\u5185\u952e\u547d\u4ee4<\/p>\n
（6）\u6267\u884c\u547d\u4ee4<\/p>\n
（7）\u5b8c\u6574\u4ee3\u7801<\/p>\n
\u00a0\u4e09\u3001\u51fd\u6570\u548c\u8fdb\u7a0b\u4e4b\u95f4\u7684\u76f8\u4f3c\u6027<\/p>\n
fork（）\u51fd\u6570\u521b\u5efa\u65b0\u7684\u5b50\u8fdb\u7a0b\u540e，\u5b50\u8fdb\u7a0b\u5982\u679c\u60f3\u6267\u884c\u4e00\u4e2a\u5168\u65b0\u7684\u7a0b\u5e8f\u5462？\u8fdb\u7a0b\u7684\u7a0b\u5e8f\u66ff\u6362\u6765\u5b8c\u6210\u8fd9\u4e2a\u529f\u80fd！\u7a0b\u5e8f\u66ff\u6362\u662f\u901a\u8fc7\u7279\u5b9a\u7684\u63a5\u53e3，\u52a0\u8f7d\u78c1\u76d8\u4e0a\u7684\u4e00\u4e2a\u5168\u65b0\u7a0b\u5e8f（\u4ee3\u7801\u548c\u7a0b\u5e8f），\u52a0\u8f7d\u5230\u8c03\u7528\u8fdb\u7a0b\u7684\u5730\u5740\u7a7a\u95f4\u4e2d！<\/p>\n
\u7528 fork \u521b\u5efa\u5b50\u8fdb\u7a0b\u540e\u6267\u884c\u7684\u662f\u548c\u7236\u8fdb\u7a0b\u76f8\u540c\u7684\u7a0b\u5e8f（\u4f46\u6709\u53ef\u80fd\u6267\u884c\u4e0d\u540c\u7684\u4ee3\u7801\u5206\u652f），\u5b50\u8fdb\u7a0b\u5f80\u5f80\u8981\u8c03\u7528\u4e00\u79cd exec \u51fd\u6570\u4ee5\u6267\u884c\u53e6\u4e00\u4e2a\u7a0b\u5e8f\u3002\u5f53\u8fdb\u7a0b\u8c03\u7528\u4e00\u79cd exec \u51fd\u6570\u65f6，\u8be5\u8fdb\u7a0b\u7684\u7528\u6237\u7a7a\u95f4\u4ee3\u7801\u548c\u6570\u636e\u5b8c\u5168\u88ab\u65b0\u7a0b\u5e8f\u66ff\u6362，\u4ece\u65b0\u7a0b\u5e8f\u7684\u542f\u52a8\u4f8b\u7a0b\u5f00\u59cb\u6267\u884c\u3002\u8c03\u7528 exec \u5e76\u4e0d\u521b\u5efa\u65b0\u8fdb\u7a0b，\u6240\u4ee5\u8c03\u7528 exec \u524d\u540e\u8be5\u8fdb\u7a0b\u7684ID\u5e76\u672a\u6539\u53d8\u3002exec\u53ea\u662f\u7528\u78c1\u76d8\u4e0a\u7684\u4e00\u4e2a\u65b0\u7a0b\u5e8f\u66ff\u6362\u4e86\u5f53\u524d\u8fdb\u7a0b\u7684\u6b63\u6587\u6bb5\u3001\u6570\u636e\u6bb5\u3001\u5806\u6bb5\u548c\u6808\u6bb5\u3002<\/p>\n
<\/p>\n
\u793a\u4f8b：<\/p>\n
#include<stdio.h>
\n#include<unistd.h><\/p>\n
int main()
\n{
\n printf("\u7a0b\u5e8f\u8fd0\u884c！\\\\n");
\n execl("\/usr\/bin\/ls", "ls", "-l", "-a", NULL);
\n printf("\u7a0b\u5e8f\u8fd0\u884c\u5b8c\u6bd5！\\\\n");
\n return 0;
\n}<\/p>\n
$ .\/proc # \u539f\u59cb\u4ee3\u7801\u4e2d\u7684\u7b2c\u4e8c\u4e2aprintf\u51fd\u6570\u88ab\u66ff\u6362，\u4e0d\u6267\u884c！
\n\u7a0b\u5e8f\u8fd0\u884c！
\ntotal 32
\ndrwxrwxr-x 2 zyt zyt 4096 Apr 18 17:13 .
\ndrwxrwxr-x 16 zyt zyt 4096 Apr 18 17:07 ..
\n-rw-rw-r– 1 zyt zyt 58 Apr 18 17:12 Makefile
\n-rwxrwxr-x 1 zyt zyt 16000 Apr 18 17:13 proc
\n-rw-rw-r– 1 zyt zyt 190 Apr 18 17:13 test.c<\/p>\n
\u4e00\u65e6\u7a0b\u5e8f\u66ff\u6362\u6210\u529f，\u5c31\u53bb\u6267\u884c\u65b0\u4ee3\u7801\u4e86，\u540e\u7eed\u7684\u539f\u59cb\u4ee3\u7801\u4e5f\u5c31\u4e0d\u5b58\u5728\u4e86（\u88ab\u8986\u76d6\u4e86）\u3002<\/p>\n
\u00a0exec* \u51fd\u6570\u53ea\u6709\u5931\u8d25\u8fd4\u56de\u503c，\u6ca1\u6709\u6210\u529f\u8fd4\u56de\u503c\u3002\u6240\u4ee5\u5bf9\u4e8eexec\u51fd\u6570\u4e0d\u7528\u5bf9\u8fd4\u56de\u503c\u505a\u5224\u65ad\u3002<\/p>\n
\u25cf \u8fd9\u4e9b\u51fd\u6570\u5982\u679c\u8c03\u7528\u6210\u529f\u5219\u52a0\u8f7d\u65b0\u7684\u7a0b\u5e8f\u4ece\u542f\u52a8\u4ee3\u7801\u5f00\u59cb\u6267\u884c，\u4e0d\u518d\u8fd4\u56de\u3002<\/p>\n
\u25cf \u5982\u679c\u8c03\u7528\u51fa\u9519\u5219\u8fd4\u56de-1，\u82e5\u6210\u529f，\u4e0d\u8fd4\u56de\u3002<\/p>\n
#include <unistd.h>
\nint execl(const char *path, const char *arg, …);
\nint execlp(const char *file, const char *arg, …);
\nint execle(const char *path, const char *arg, …,char *const envp[]);
\nint execv(const char *path, char *const argv[]);
\nint execvp(const char *file, char *const argv[]);
\nint execve(const char *path, char *const argv[], char *const envp[]);
\nint fexecve(int fd, char *const argv[], char *const envp[]); <\/p>\n
pathname\u5c31\u662f\u53d6\u3010\u8def\u5f84\u540d+\u7a0b\u5e8f\u3011\u4f5c\u4e3a\u53c2\u6570；filename\u5c31\u662f\u6587\u4ef6\u540d\u4f5c\u4e3a\u53c2\u6570，\u5f53\u6307\u5b9afilename\u4f5c\u4e3a\u53c2\u6570\u65f6：<\/p>\n
\u25cf \u5982\u679cfilename\u4e2d\u5305\u542b\u201c\/\u201d，\u5219\u5c06\u5176\u89c6\u4e3a\u8def\u5f84\u540d\u3002<\/p>\n
\u25cf \u5426\u5219\u5c31\u6309\u7167PATH\u73af\u5883\u53d8\u91cf，\u5728\u5b83\u6240\u6307\u5b9a\u7684\u5404\u76ee\u5f55\u4e2d\u641c\u7d22\u53ef\u6267\u884c\u6587\u4ef6\u3002\u3010\u4e0d\u77e5\u9053PATH\u73af\u5883\u53d8\u91cf\u7684\u8bdd\u770b\u524d\u6587：\u6df1\u5165\u6d45\u51fa：\u73af\u5883\u53d8\u91cf\u4e0e\u8fdb\u7a0b\u5730\u5740\u7a7a\u95f4\u7684\u6838\u5fc3\u673a\u5236-CSDN\u535a\u5ba2\u3011<\/p>\n
\u51fd\u6570execl\u3001execlp \u548c execle \u8981\u6c42\u65b0\u7a0b\u5e8f\u7684\u6bcf\u4e00\u4e2a\u547d\u4ee4\u884c\u53c2\u6570\u90fd\u8bf4\u660e\u4e00\u4e2a\u5355\u72ec\u7684\u53c2\u6570\u3002\u8fd9\u79cd\u53c2\u6570\u8868\u4ee5\u7a7a\u6307\u9488\u7ed3\u5c3e\u3002\u5bf9execl\u3001execlp \u548c execle\u4e09\u4e2a\u51fd\u6570\u8868\u793a\u547d\u4ee4\u884c\u53c2\u6570\u7684\u4e00\u822c\u65b9\u6cd5：<\/p>\n
char *arg(), char *argl, …, char *argn, (char *)0 <\/p>\n
\u00a0\u8fd9\u79cd\u8bed\u6cd5\u663e\u793a\u7684\u8bf4\u660e\u4e86\u6700\u540e\u4e00\u4e2a\u547d\u4ee4\u884c\u53c2\u6570\u4e4b\u540e\u8ddf\u4e86\u4e00\u4e2a\u7a7a\u6307\u9488\u3002\u5982\u679c\u7528\u5e38\u91cf0\u6765\u8868\u793a\u4e00\u4e2a\u7a7a\u6307\u9488，\u5219\u5fc5\u987b\u5c06\u5b83\u5f3a\u5236\u8f6c\u5316\u6210\u4e3a\u4e00\u4e2a\u6307\u9488：\u5426\u5219\u5b83\u5c06\u88ab\u89e3\u91ca\u6210\u6574\u5f62\u53c2\u6570\u3002\u5982\u679c\u4e00\u4e2a\u6574\u5f62\u6570\u7684\u957f\u5ea6\u4e0echar*\u7684\u957f\u5ea6\u4e0d\u540c，\u90a3\u4e48exec\u51fd\u6570\u7684\u5b9e\u9645\u53c2\u6570\u5c06\u51fa\u9519\u3002<\/p>\n
\u5bf9\u4e8e\u5176\u4f59\u76844\u4e2a\u51fd\u6570，\u5219\u5e94\u5148\u6784\u9020\u4e00\u4e2a\u6307\u5411\u5404\u53c2\u6570\u7684\u6307\u9488\u6570\u7ec4，\u7136\u540e\u5c06\u8be5\u6570\u7ec4\u6307\u9488\u5730\u5740\u4f5c\u4e3a\u8fd94\u4e2a\u51fd\u6570\u7684\u53c2\u6570（\u5efa\u7acbargv）\u3002<\/p>\n
\u4ee5e\u7ed3\u5c3e\u7684\u4e09\u4e2a\u51fd\u6570（execle\u3001execve\u3001fexecve）\u53ef\u4ee5\u4f20\u9012\u4e00\u4e2a\u6307\u5411\u73af\u5883\u5b57\u7b26\u4e32\u6307\u9488\u6570\u7ec4\u7684\u6307\u9488\u3002\u5728ISO C\u539f\u578b（\u56fd\u9645\u6807\u51c6\u5316\u7ec4\u7ec7\u5236\u5b9a\u7684C\u8bed\u8a00\u6807\u51c6）\u4e4b\u524d，execle\u7684\u53c2\u6570\u662f：<\/p>\n
char *pathname, char *arg(), …, char *argn, (char *)0, char *envp[] <\/p>\n
\u4ece\u4e2d\u53ef\u89c1，\u6700\u540e\u4e00\u4e2a\u53c2\u6570\u662f\u6307\u5411\u73af\u5883\u5b57\u7b26\u4e32\u7684\u5404\u5b57\u7b26\u6307\u9488\u6784\u6210\u7684\u6570\u7ec4\u7684\u6307\u9488\u3002\u800c\u5728ISO C\u539f\u578b\u4e2d，\u6240\u6709\u547d\u4ee4\u884c\u53c2\u6570\u3001\u7a7a\u6307\u9488\u548cenvp\u6307\u9488\u90fd\u662f\u7528\u7701\u7565\u53f7（…）\u8868\u793a\u3002\u00a0<\/p>\n
\u5176\u4ed6\u56db\u4e2a\u51fd\u6570，\u5219\u4f7f\u7528\u8c03\u7528\u8fdb\u7a0b\u4e2d\u7684environ\u53d8\u91cf\u4e3a\u65b0\u7a0b\u5e8f\u590d\u5236\u73b0\u6709\u7684\u73af\u5883\u3002\u901a\u5e38，\u4e00\u4e2a\u8fdb\u7a0b\u5141\u8bb8\u5c06\u5176\u73af\u5883\u4f20\u64ad\u7ed9\u5176\u5b50\u8fdb\u7a0b，\u4f46\u6709\u65f6\u4e5f\u6709\u8fd9\u79cd\u60c5\u51b5，\u8fdb\u7a0b\u60f3\u4e3a\u5b50\u8fdb\u7a0b\u6307\u5b9a\u67d0\u4e00\u4e2a\u786e\u5b9a\u7684\u73af\u5883，\u53ef\u4ee5\u76f4\u63a5\u7528putenv（）\u51fd\u6570\u3010\u6dfb\u52a0\u6216\u4fee\u6539\u73af\u5883\u53d8\u91cf，\u5b83\u63a5\u53d7\u4e00\u4e2a\u5f62\u5f0f\u4e3a "name=value" \u7684\u5b57\u7b26\u4e32，\u5e76\u5c06\u5176\u6dfb\u52a0\u5230\u5f53\u524d\u8fdb\u7a0b\u7684\u73af\u5883\u53d8\u91cf\u5217\u8868\u4e2d\u3011；\u6216\u8005\u901a\u8fc7\u7b2c\u4e09\u65b9\u53d8\u91cfenviron\u3002<\/p>\n
\u8fd97\u4e2a\u51fd\u6570\u7684\u53c2\u6570\u5f88\u96be\u8bb0\u5fc6\u3002\u51fd\u6570\u540d\u7684\u5b57\u7b26\u4f1a\u7ed9\u6211\u4eec\u4e00\u4e9b\u5e2e\u52a9\u3002<\/p>\n
\u25cf \u5b57\u6bcdp\u8868\u793a\u8be5\u51fd\u6570\u53d6filename\u4f5c\u4e3a\u53c2\u6570，\u5e76\u4e14\u7528PATH\u73af\u5883\u53d8\u91cf\u5bfb\u627e\u53ef\u6267\u884c\u6587\u4ef6\u3002<\/p>\n
\u25cf \u5b57\u6bcdl\u8868\u793a\u8be5\u51fd\u6570\u53d6\u4e00\u4e2a\u53c2\u6570\u8868，\u53c2\u6570\u4ee5\u53ef\u53d8\u53c2\u6570\u5217\u8868\u7684\u5f62\u5f0f\u4f20\u9012\u3002\u00a0<\/p>\n
\u25cf \u5b57\u6bcdv\u4e0e\u5b57\u6bcdl\u4e92\u65a5，v\u8868\u793a\u8be5\u51fd\u6570\u53d6\u4e86\u4e00\u4e2aargv[]\u77e2\u91cf，\u53c2\u6570\u4ee5\u5b57\u7b26\u6307\u9488\u6570\u7ec4\u7684\u5f62\u5f0f\u4f20\u9012\u3002<\/p>\n
\u25cf \u5b57\u6bcde\u8868\u793a\u8be5\u51fd\u6570\u53d6envp[]\u6570\u7ec4，\u81ea\u5df1\u7ef4\u62a4\u73af\u5883\u53d8\u91cf，\u800c\u4e0d\u4f7f\u7528\u5f53\u524d\u73af\u5883\u3002<\/p>\n
![\"\"](\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250426053027-680c6f731e34c.png\")
<\/p>\n
\u8c03\u7528\u793a\u4f8b\u5982\u4e0b：<\/p>\n
#include <unistd.h><\/p>\n
int main() {
\n char *const argv[] = {"ps", "-ef", NULL};
\n char *const envp[] = {"PATH=\/bin:\/usr\/bin", "TERM=console", NULL};<\/p>\n
\/\/ \u4f7f\u7528 execl \u6267\u884c \/bin\/ps \u547d\u4ee4，\u9700\u8981\u5b8c\u6574\u8def\u5f84
\n execl("\/bin\/ps", "ps", "-ef", NULL);<\/p>\n
\/\/ \u4f7f\u7528 execlp \u6267\u884c ps \u547d\u4ee4，\u5e26 p \u7684，\u53ef\u4ee5\u4f7f\u7528\u73af\u5883\u53d8\u91cf PATH，\u65e0\u9700\u5199\u5168\u8def\u5f84
\n execlp("ps", "ps", "-ef", NULL);<\/p>\n
\/\/ \u4f7f\u7528 execle \u6267\u884c ps \u547d\u4ee4，\u5e26 e \u7684，\u9700\u8981\u81ea\u5df1\u7ec4\u88c5\u73af\u5883\u53d8\u91cf
\n execle("\/bin\/ps", "ps", "-ef", NULL, envp);<\/p>\n
\/\/ \u4f7f\u7528 execv \u6267\u884c \/bin\/ps \u547d\u4ee4，\u9700\u8981\u5b8c\u6574\u8def\u5f84
\n execv("\/bin\/ps", argv);<\/p>\n
\/\/ \u4f7f\u7528 execvp \u6267\u884c ps \u547d\u4ee4，\u5e26 p \u7684，\u53ef\u4ee5\u4f7f\u7528\u73af\u5883\u53d8\u91cf PATH，\u65e0\u9700\u5199\u5168\u8def\u5f84
\n execvp("ps", argv);<\/p>\n
\/\/ \u4f7f\u7528 execve \u6267\u884c \/bin\/ps \u547d\u4ee4，\u5e26 e \u7684，\u9700\u8981\u81ea\u5df1\u7ec4\u88c5\u73af\u5883\u53d8\u91cf
\n execve("\/bin\/ps", argv, envp);<\/p>\n
exit(0);
\n} <\/p>\n
\u5728\u5f88\u591aUnix\u7684\u5b9e\u73b0\u4e2d，\u8fd97\u4e2a\u51fd\u6570\u4e2d\u53ea\u6709execve\u662f\u5185\u6838\u7684\u7cfb\u7edf\u8c03\u7528\u3002\u53e6\u59166\u4e2a\u53ea\u662f\u5e93\u51fd\u6570，\u5b83\u4eec\u6700\u7ec8\u90fd\u8981\u8c03\u7528\u8be5\u7cfb\u7edf\u8c03\u7528\u3002<\/span><\/span>\u8fd97\u4e2a\u51fd\u6570\u4e4b\u95f4\u7684\u5173\u7cfb\u5982\u56fe：<\/p>\n \u8003\u8651\u4e0b\u9762\u8fd9\u4e2a\u4e0eshell\u7684\u4e92\u52a8：<\/p>\n [root@localhost epoll]# ls [root@localhost epoll]# ps \u7528\u4e0b\u56fe\u7684\u65f6\u95f4\u8f74\u6765\u8868\u793a\u4e8b\u4ef6\u7684\u53d1\u751f\u6b21\u5e8f\u3002\u5176\u4e2d\u65f6\u95f4\u4ece\u5de6\u5411\u53f3，shell\u7531\u6807\u8bc6\u4e3ash\u7684\u65b9\u5757\u8868\u793a，\u5b83\u968f\u7740\u65f6\u95f4\u7684\u6d41\u901d\u4ece\u5de6\u5411\u53f3\u79fb\u52a8\u3002shell\u4ece\u7528\u6237\u8bfb\u5165\u5b57\u7b26\u4e32\u201cls\u201d\u3002shell\u5efa\u7acb\u4e00\u4e2a\u65b0\u7684\u8fdb\u7a0b，\u7136\u540e\u5728\u90a3\u4e2a\u8fdb\u7a0b\u4e2d\u8fd0\u884cls\u7a0b\u5e8f\u5e76\u7b49\u5f85\u90a3\u4e2a\u8fdb\u7a0b\u7ed3\u675f\u3002\u00a0 \u7136\u540eshell\u8bfb\u53d6\u65b0\u7684\u4e00\u884c\u8f93\u5165，\u5efa\u7acb\u4e00\u4e2a\u65b0\u7684\u8fdb\u7a0b，\u5728\u8fd9\u4e2a\u8fdb\u7a0b\u4e2d\u8fd0\u884c\u7a0b\u5e8f\u5e76\u7b49\u5f85\u8fd9\u4e2a\u8fdb\u7a0b\u7ed3\u675f\u3002<\/p>\n \u6240\u4ee5，\u5b9e\u73b0\u4e00\u4e2a\u81ea\u5b9a\u4e49shell\u9700\u8981\u5faa\u73af\u4ee5\u4e0b\u8fc7\u7a0b：<\/p>\n （1）\u83b7\u53d6\u547d\u4ee4\u884c<\/p>\n （2）\u89e3\u6790\u547d\u4ee4\u884c<\/p>\n （3）\u5efa\u7acb\u4e00\u4e2a\u5b50\u8fdb\u7a0b（fork）<\/p>\n （4）\u66ff\u6362\u5b50\u8fdb\u7a0b（execvp）<\/p>\n （5）\u7236\u8fdb\u7a0b\u7b49\u5f85\u5b50\u8fdb\u7a0b\u9000\u51fa（wait）<\/p>\n \u8981\u5b9e\u73b0\u4e00\u4e2a\u81ea\u5b9a\u4e49 Shell，\u73af\u5883\u53d8\u91cf\u7684\u5904\u7406\u662f\u5173\u952e\u90e8\u5206\u3002\u6b63\u5e38\u60c5\u51b5shell\u542f\u52a8\u8981\u4ece\u7cfb\u7edf\u4e2d\u83b7\u53d6\u73af\u5883\u53d8\u91cf，\u800c\u6211\u4eec\u81ea\u5b9a\u4e49shell\u7684\u73af\u5883\u53d8\u91cf\u4fe1\u606f\u8981\u4ece\u7236shell\u4e2d\u83b7\u53d6\u3002<\/p>\n \u624b\u52a8\u83b7\u53d6：\u5728 C \u4e2d\u53ef\u4ee5\u901a\u8fc7 extern char **environ \u8bbf\u95ee\u7ee7\u627f\u7684\u73af\u5883\u53d8\u91cf\u3002\u5c06\u7236Shell\u7684\u73af\u5883\u53d8\u91cf\u9010\u6761\u590d\u5236\u5230g_env\u4e2d，\u7136\u540e\u5c06g_env\u4e2d\u7684\u53d8\u91cf\u6dfb\u52a0\u5230\u5f53\u524d\u8fdb\u7a0b\u7684\u73af\u5883\u53d8\u91cf\u8868\u3002\u3010\u6ce8\u610f：（\u8fd9\u91cc\u4f7f\u7528\u4e86putenv() \u51fd\u6570）\u6b64\u540eg_env[i]\u7684\u5185\u5b58\u7531\u7cfb\u7edf\u7ba1\u7406，\u4e0d\u80fd\u518d\u624b\u52a8free！Unix\/Linux\u7cfb\u7edf\u63d0\u4f9b\u7684\u5168\u5c40\u53d8\u91cf，\u6307\u5411\u5f53\u524d\u8fdb\u7a0b\u7684\u73af\u5883\u53d8\u91cf\u8868，\u3011<\/p>\n \/\/ \u73af\u5883\u53d8\u91cf\u8868 \/\/ \u4ece\u7236shell1\u83b7\u53d6\u73af\u5883\u53d8\u91cf\u8868，\u672c\u6765\u662f\u8981\u4ece\u914d\u7f6e\u6587\u4ef6\u83b7\u53d6\u7684 \/\/ 1.\u83b7\u53d6\u73af\u5883\u53d8\u91cf \/\/ 2.\u83b7\u53d6\u5230\u7684\u73af\u5883\u53d8\u91cf\u5bfc\u5165shell\u7684\u8868\u4e2d \u63d0\u793a\u7b26\u683c\u5f0f：[\u7528\u6237\u540d@\u4e3b\u673a\u540d:\u5f53\u524d\u76ee\u5f55\u7684\u57fa\u540d]#\u00a0<\/p>\n \u2460 MakeCommandline() \u4e2d\u4f7f\u7528 snprintf() \u683c\u5f0f\u5316\u63d0\u793a\u7b26：\u3010format：\u683c\u5f0f\u5316\u5b57\u7b26\u4e32，\u7528\u4e8e\u6307\u5b9a\u5982\u4f55\u683c\u5f0f\u5316\u540e\u7eed\u7684\u53c2\u6570\u3011\u3010…：\u53ef\u53d8\u53c2\u6570\u5217\u8868，\u6839\u636e format \u7684\u8981\u6c42\u63d0\u4f9b\u76f8\u5e94\u7684\u503c\u3011<\/p>\n int snprintf(char *str, size_t size, const char *format, …); <\/p>\n \u2461 PrintCommandline() \u6253\u5370\u547d\u4ee4\u884c\u63d0\u793a\u7b26：fflush\u7528\u6765\u786e\u4fdd\u63d0\u793a\u7b26\u7acb\u5373\u663e\u793a（\u5c24\u5176\u5728\u65e0\u6362\u884c\u7b26\u65f6）\u3002<\/p>\n #define COMMAND_SIZE 1024 \/\/ shell\u5b9a\u4e49\u7684\u5168\u5c40\u53d8\u91cf<\/p>\n char cwd[1019]; const char *GetUserName() const char *GetHostName() const char *GetPwd() \/\/ \u5bf9\u8def\u5f84\u505a\u5305\u88c5，\u53ea\u663e\u793a\u5f53\u524d\u4f4d\u7f6e \/\/ \u5236\u4f5c\u547d\u4ee4\u884c\u63d0\u793a\u7b26 \/\/ \u6253\u5370\u547d\u4ee4\u884c\u63d0\u793a\u7b26 GetCommandline() \u4ece\u6807\u51c6\u8f93\u5165\u8bfb\u53d6\u4e00\u884c\u7528\u6237\u8f93\u5165\u7684\u547d\u4ee4\u3002<\/p>\n fgets() \u662f\u4e00\u4e2a\u5728 C \u8bed\u8a00\u4e2d\u7528\u4e8e\u4ece\u6587\u4ef6\u6d41\u4e2d\u8bfb\u53d6\u5b57\u7b26\u4e32\u7684\u51fd\u6570，\u5c5e\u4e8e\u6807\u51c6\u5e93 <stdio.h> \u4e2d\u7684\u51fd\u6570\u3002\u5b83\u80fd\u591f\u4ece\u6307\u5b9a\u7684\u6587\u4ef6\u6d41\u4e2d\u8bfb\u53d6\u4e00\u884c\u6570\u636e，\u5e76\u5c06\u5176\u5b58\u50a8\u5230\u76ee\u6807\u7f13\u51b2\u533a\u4e2d，\u540c\u65f6\u53ef\u4ee5\u9650\u5236\u8bfb\u53d6\u7684\u6700\u5927\u5b57\u7b26\u6570，\u4ece\u800c\u907f\u514d\u7f13\u51b2\u533a\u6ea2\u51fa\u3002<\/p>\n char* fgets(char* str, int size, FILE* stream); <\/p>\n \u4f46 fgets() \u4f1a\u4fdd\u7559\u8f93\u5165\u4e2d\u7684\u6362\u884c\u7b26，\u6240\u4ee5\u8c03\u7528\u540e\u8981\u6e05\u7406\u6362\u884c\u7b26\u3002<\/p>\n \/\/ \u83b7\u53d6\u7528\u6237\u8f93\u5165\u547d\u4ee4 if(c == NULL) return 1; if(strlen(out) == 0) return false;\/\/ \u4ec0\u4e48\u90fd\u6ca1\u8f93\u5165 \u51fd\u6570\u5b9e\u73b0：\u547d\u4ee4\u884c\u5b57\u7b26\u4e32\u7684\u89e3\u6790，\u5c06\u7528\u6237\u8f93\u5165\u7684\u547d\u4ee4\u884c（\u5982 "ls -a -l"）\u62c6\u5206\u4e3a \u53c2\u6570\u6570\u7ec4 g_argv，\u5e76\u8bb0\u5f55\u53c2\u6570\u4e2a\u6570 g_argc\u3002<\/p>\n strtok() \u662f\u4e00\u4e2a\u5728 C \u8bed\u8a00\u4e2d\u7528\u4e8e\u5b57\u7b26\u4e32\u5206\u5272\u7684\u51fd\u6570，\u5c5e\u4e8e\u6807\u51c6\u5e93 <string.h> \u4e2d\u7684\u51fd\u6570\u3002\u5b83\u53ef\u4ee5\u6839\u636e\u6307\u5b9a\u7684\u5206\u9694\u7b26\u5c06\u5b57\u7b26\u4e32\u5206\u5272\u6210\u591a\u4e2a\u5b50\u5b57\u7b26\u4e32，\u5e76\u4e14\u5728\u591a\u6b21\u8c03\u7528\u4e2d\u9010\u4e2a\u8fd4\u56de\u8fd9\u4e9b\u5b50\u5b57\u7b26\u4e32\u3002<\/p>\n char* strtok(char* str, const char* delim); <\/p>\n \u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6，str \u662f\u6307\u5411\u8981\u5206\u5272\u7684\u539f\u59cb\u5b57\u7b26\u4e32\u7684\u6307\u9488\u3002 \u5728\u540e\u7eed\u8c03\u7528\u4e2d，str \u5e94\u8be5\u4f20\u5165 NULL，\u8868\u793a\u7ee7\u7eed\u5206\u5272\u4e0a\u4e00\u6b21\u8c03\u7528\u540e\u5269\u4f59\u7684\u90e8\u5206\u3002<\/span><\/span><\/p>\n \/\/ \u5168\u5c40\u7684\u547d\u4ee4\u884c\u53c2\u6570\u8868 \/\/ 3. \u547d\u4ee4\u884c\u5206\u6790 CheckAndExecBuiltin() \u68c0\u67e5\u662f\u5426\u4e3a\u5185\u5efa\u547d\u4ee4\u3002CD()\u00a0\u5b9e\u73b0\u76ee\u5f55\u5207\u6362（cd \u547d\u4ee4），Echo()\u00a0\u5b9e\u73b0 echo \u547d\u4ee4\u3002<\/p>\n chdir() \u662f\u4e00\u4e2a\u5728 C \u8bed\u8a00\u4e2d\u7528\u4e8e\u66f4\u6539\u5f53\u524d\u5de5\u4f5c\u76ee\u5f55\u7684\u51fd\u6570，\u5c5e\u4e8e\u6807\u51c6\u5e93 <unistd.h> \u4e2d\u7684\u51fd\u6570（\u5728 POSIX \u7cfb\u7edf\u4e2d）\u3002\u5b83\u5141\u8bb8\u7a0b\u5e8f\u52a8\u6001\u5730\u6539\u53d8\u5f53\u524d\u8fdb\u7a0b\u7684\u5de5\u4f5c\u76ee\u5f55\u3002<\/p>\n \/\/ \u6700\u540e\u4e00\u4e2a\u7a0b\u5e8f\u9000\u51fa\u7801 \/\/ \u5168\u5c40\u7684\u547d\u4ee4\u884c\u53c2\u6570\u8868 \/\/ \u5185\u952e\u547d\u4ee4 if(g_argc == 1) \/\/ \u53ea\u6709\u4e00\u4e2acd\u65f6 bool Echo() \/\/ 4. \u68c0\u6d4b\u5e76\u6267\u884c\u5185\u952e\u547d\u4ee4 Execute() \u5b9e\u73b0\u4e86 Shell \u4e2d\u5916\u90e8\u547d\u4ee4\u7684\u6267\u884c，\u6838\u5fc3\u662f\u901a\u8fc7 fork() \u521b\u5efa\u5b50\u8fdb\u7a0b，\u5e76\u5728\u5b50\u8fdb\u7a0b\u4e2d\u8c03\u7528 execvp \u6267\u884c\u76ee\u6807\u547d\u4ee4（\u81ea\u5b9a\u4e49shell），\u7236\u8fdb\u7a0b\u5219\u7b49\u5f85\u5b50\u8fdb\u7a0b\u7ed3\u675f\u5e76\u8bb0\u5f55\u5176\u9000\u51fa\u72b6\u6001\u3002<\/p>\n \/\/ 5.\u6267\u884c\u547d\u4ee4 #include<iostream> #define COMMAND_SIZE 1024 \/\/ shell\u5b9a\u4e49\u7684\u5168\u5c40\u53d8\u91cf<\/p>\n \/\/ \u5168\u5c40\u7684\u547d\u4ee4\u884c\u53c2\u6570\u8868 char cwd[1019]; \/\/ \u73af\u5883\u53d8\u91cf\u8868 \/\/ \u6700\u540e\u4e00\u4e2a\u7a0b\u5e8f\u9000\u51fa\u7801 const char *GetUserName() const char *GetHostName() const char *GetPwd() const char *GetHome() \/\/ \u5bf9\u8def\u5f84\u505a\u5305\u88c5 \/\/ \u5236\u4f5c\u547d\u4ee4\u884c\u63d0\u793a\u7b26 \/\/ \u6253\u5370\u547d\u4ee4\u884c\u63d0\u793a\u7b26 \/\/ \u83b7\u53d6\u7528\u6237\u8f93\u5165\u547d\u4ee4 if(c == NULL) return 1; if(strlen(out) == 0) return false;\/\/ \u4ec0\u4e48\u90fd\u6ca1\u8f93\u5165 \/\/ 3. \u547d\u4ee4\u884c\u5206\u6790 void PrintArray() \/\/ \u4ece\u7236shell1\u83b7\u53d6\u73af\u5883\u53d8\u91cf\u8868，\u672c\u6765\u662f\u8981\u4ece\u914d\u7f6e\u6587\u4ef6\u83b7\u53d6\u7684 \/\/ 1.\u83b7\u53d6\u73af\u5883\u53d8\u91cf \/\/ 2.\u83b7\u53d6\u5230\u7684\u73af\u5883\u53d8\u91cf\u5bfc\u5165shell\u7684\u8868\u4e2d \/\/ \u5185\u952e\u547d\u4ee4 if(g_argc == 1) \/\/ \u53ea\u6709\u4e00\u4e2acd\u65f6 bool Echo() \/\/ 4. \u68c0\u6d4b\u5e76\u6267\u884c\u5185\u952e\u547d\u4ee4 \/\/ 5.\u6267\u884c\u547d\u4ee4 void FreeEnvMemory() { int main() \/\/ 2. \u83b7\u53d6\u8f93\u5165\u7684\u547d\u4ee4 \/\/ 3. \u547d\u4ee4\u884c\u5206\u6790, \u5b57\u7b26\u4e32\u62c6\u5206\u6210\u591a\u4e2a\u5143\u7d20 \/\/ 4.\u68c0\u6d4b\u5e76\u6267\u884c\u5185\u5efa\u547d\u4ee4 \/\/ 5. \u6267\u884c\u547d\u4ee4 \u4e00\u4e2aC\u7a0b\u5e8f\u6709\u5f88\u591a\u51fd\u6570\u7ec4\u6210\u3002\u4e00\u4e2a\u51fd\u6570\u53ef\u4ee5\u8c03\u7528\u53e6\u4e00\u4e2a\u51fd\u6570，\u540c\u65f6\u4f20\u9012\u7ed9\u5b83\u4e00\u4e9b\u53c2\u6570\u3002\u88ab\u8c03\u7528\u7684\u51fd\u6570\u6267\u884c\u4e00\u5b9a\u7684\u64cd\u4f5c，\u7136\u540e\u8fd4\u56de\u4e00\u4e2a\u503c\u3002\u6bcf\u4e2a\u51fd\u6570\u90fd\u6709\u4ed6\u7684\u5c40\u90e8\u53d8\u91cf，\u4e0d\u540c\u7684\u51fd\u6570\u901a\u8fc7 call\/return \u7cfb\u7edf\u8fdb\u884c\u901a\u4fe1\u3002\u8fd9\u79cd\u901a\u8fc7\u53c2\u6570\u548c\u8fd4\u56de\u503c\u5728\u62e5\u6709\u79c1\u6709\u6570\u636e\u7684\u51fd\u6570\u95f4\u901a\u4fe1\u7684\u6a21\u5f0f\u662f\u7ed3\u6784\u5316\u7a0b\u5e8f\u8bbe\u8ba1\u7684\u57fa\u7840\u3002Linux \u9f13\u52b1\u5c06\u8fd9\u79cd\u5e94\u7528\u4e8e\u7a0b\u5e8f\u4e4b\u5185\u7684\u6a21\u5f0f\u6269\u5c55\u5230\u7a0b\u5e8f\u4e4b\u95f4\u3002\u5982\u4e0b\u56fe：<\/p>\n \u4e00\u4e2aC\u7a0b\u5e8f\u53ef\u4ee5 fork\/exec \u53e6\u4e00\u4e2a\u7a0b\u5e8f，\u5e76\u4f20\u7ed9\u5b83\u4e00\u4e9b\u53c2\u6570\u3002\u8fd9\u4e2a\u88ab\u8c03\u7528\u7684\u7a0b\u5e8f\u6267\u884c\u4e00\u5b9a\u7684\u64cd\u4f5c，\u7136\u540e\u901a\u8fc7 exit(n) \u6765\u8fd4\u56de\u503c\u3002\u8c03\u7528\u5b83\u7684\u8fdb\u7a0b\u53ef\u4ee5\u901a\u8fc7 wait(&ret) \u6765\u83b7\u53d6 exit \u7684\u8fd4\u56de\u503c\u3002<\/p>\n","protected":false},"excerpt":{"rendered":" \u6587\u7ae0\u6d4f\u89c8\u9605\u8bfb1.3k\u6b21\uff0c\u70b9\u8d5e43\u6b21\uff0c\u6536\u85cf52\u6b21\u3002\u672c\u6587\u6df1\u5165\u63a2\u8ba8\u8fdb\u7a0b\u66ff\u6362\u539f\u7406\u4e0e\u5b9e\u73b0\uff0c\u89e3\u6790 exec \u51fd\u6570\u7684\u5173\u952e\u7279\u6027\uff0c\u540c\u65f6\u8bbe\u8ba1\u5e76\u5b9e\u73b0\u4e00\u4e2a\u81ea\u5b9a\u4e49 Shell \u547d\u4ee4\u884c\u89e3\u91ca\u5668\uff0c\u63ed\u793a\u51fd\u6570\u8c03\u7528\u4e0e\u8fdb\u7a0b\u901a\u4fe1\u7684\u5185\u5728\u76f8\u4f3c\u6027\uff0c\u52a9\u529b\u8bfb\u8005\u638c\u63e1 Unix \u73af\u5883\u4e0b\u7684\u6838\u5fc3\u7f16\u7a0b\u6280\u5de7\u3002<\/p>\n","protected":false},"author":2,"featured_media":33075,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[58,103,43,44],"topic":[],"class_list":["post-33080","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-server","tag-linux","tag-ubuntu","tag-43","tag-44"],"yoast_head":"\n![\"\"](\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250426053027-680c6f736d89d.png\")
<\/p>\n\u00a0\u4e8c\u3001\u81ea\u5b9a\u4e49shell\u547d\u4ee4\u884c\u89e3\u91ca\u5668<\/h2>\n
1\u3001\u5b9e\u73b0\u539f\u7406<\/h3>\n
\nclient.cpp readme.md server.cpp utility.h<\/p>\n
\n PID TTY TIME CMD
\n 3451 pts\/0 00:00:00 bash
\n 3514 pts\/0 00:00:00 ps <\/p>\n![\"\"](\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250426053027-680c6f73ad510.png\")
<\/p>\n2\u3001\u5b9e\u73b0\u4ee3\u7801<\/h3>\n
（1）\u83b7\u53d6\u73af\u5883\u53d8\u91cf<\/h4>\n
\n#define MAX_ENVS 1024
\nchar *g_env[MAX_ENVS];
\nint g_envs = 0;<\/p>\n
\nvoid InitEnv()
\n{
\n extern char **environ;
\n memset(g_env, 0, sizeof(g_env)); \/\/ \u521d\u59cb\u5316
\n g_envs = 0;<\/p>\n
\n for(int i = 0; environ[i]; i++)
\n {
\n \/\/ (1)\u7533\u8bf7\u7a7a\u95f4
\n g_env[i] = (char*)malloc(strlen(environ[i])+1);
\n \/\/ (2)\u62f7\u8d1d\u5230\u6211\u4eec\u7684\u73af\u5883\u53d8\u91cf\u8868
\n strcpy(g_env[i], environ[i]);
\n g_envs++;
\n }
\n \/\/ \u6d4b\u8bd5：\u6dfb\u52a0\u4e86\u4e00\u4e2a\u65b0\u7684\u73af\u5883\u53d8\u91cf
\n g_env[g_envs++] = (char*)"HAHA=for_test";
\n g_env[g_envs] = NULL; \/\/ \u8868\u7684\u6700\u540e\u4e00\u4e2a\u6210\u5458\u5fc5\u987b\u662fNULL<\/p>\n
\n for(int i = 0; g_env[i]; i++)
\n {
\n putenv(g_env[i]);
\n }
\n} <\/p>\n（2）\u8f93\u51fa\u547d\u4ee4\u884c\u63d0\u793a\u7b26<\/h4>\n
\n#define HOSTNAME_MAX 1024
\n#define FORMAT "[%s@%s:%s]# "<\/p>\n
\nchar cwdenv[1024]; <\/p>\n
\n{
\n const char * name = getenv("USER");
\n return name == NULL ? "None" : name;
\n}<\/p>\n
\n{
\n char hostname[HOSTNAME_MAX];
\n return (gethostname(hostname, HOSTNAME_MAX) == -1) ? "None" : hostname;
\n}<\/p>\n
\n{
\n \/\/const char * pwd = getenv("PWD");
\n const char *pwd = getcwd(cwd, sizeof(cwd)); \/\/ \u901a\u8fc7\u7cfb\u7edf\u8c03\u7528\u83b7\u53d6
\n if(pwd != NULL)
\n { \/\/ \u628a\u81ea\u5df1\u7684\u73af\u5883\u53d8\u91cf\u5bfc\u7ed9\u8fdb\u7a0b
\n snprintf(cwdenv, sizeof(cwdenv), "PWD=%s", cwd);
\n putenv(cwdenv);
\n }
\n return pwd == NULL ? "None" : pwd;
\n}<\/p>\n
\nstd::string DirName(const char *pwd)
\n{
\n#define SLASH "\/"
\n std::string dir = pwd;
\n if(dir == SLASH) return SLASH;
\n auto pos = dir.rfind(SLASH);
\n if(pos == std::string::npos) return "BUG";
\n return dir.substr(pos+1);
\n}<\/p>\n
\nvoid MakeCommandline(char cmd_prompt[], int size)
\n{
\n \/\/ \u8bbe\u7f6e\u5f0f\u5316\u8f93\u5165
\n snprintf(cmd_prompt, size, FORMAT, GetUserName(), GetHostName(), DirName(GetPwd()).c_str());
\n \/\/snprintf(cmd_prompt, size, FORMAT, GetUserName(), GetHostName(), GetPwd());
\n}<\/p>\n
\nvoid PrintCommandline()
\n{
\n char prompt[COMMAND_SIZE];
\n MakeCommandline(prompt, COMMAND_SIZE);
\n printf("%s", prompt);
\n fflush(stdout);
\n} <\/p>\n（3）\u83b7\u53d6\u7528\u6237\u8f93\u5165\u7684\u547d\u4ee4<\/h4>\n
\nbool GetCommandline(char *out, int size)
\n{
\n \/\/ \u4ece\u6807\u51c6\u8f93\u5165\u6d41\u83b7\u53d6\u547d\u4ee4，\u5176\u5b9e\u5c31\u662f\u5b57\u7b26\u4e32
\n char* c = fgets(out, size, stdin);<\/p>\n
\n out[strlen(out)-1] = '\\\\0'; \/\/ \u6e05\u7406\\\\n, \u81f3\u5c11\u4f1a\u6309\u4e00\u6b21\u56de\u8f66，\u6240\u4ee5\u4e0d\u4f1a\u51fa\u9519<\/p>\n
\n return true;
\n} <\/p>\n（4）\u547d\u4ee4\u884c\u5206\u6790<\/h4>\n
\n#define MAXARGC 128
\nchar *g_argv[MAXARGC];
\nint g_argc = 0;<\/p>\n
\nbool CommandParse(char *commandline)
\n{
\n \/\/ "ls -a -l" -> "ls" "-a" "-l"
\n \/\/ \u5b57\u7b26\u4e32\u5207\u5272 strtok()\u51fd\u6570
\n#define SEP " "
\n g_argc = 0;
\n \/\/ \u7b2c\u4e00\u6b21\u8c03\u7528：\u4f20\u5165\u8981\u5206\u5272\u7684\u5b57\u7b26\u4e32\u548c\u5206\u9694\u7b26
\n g_argv[g_argc++] = strtok(commandline, SEP);
\n \/\/ \u540e\u7eed\u8c03\u7528：\u4f20\u5165 NULL \u548c\u5206\u9694\u7b26，\u7ee7\u7eed\u5206\u5272\u540c\u4e00\u5b57\u7b26\u4e32
\n while(g_argv[g_argc++] = strtok(NULL, SEP));
\n g_argc–; \/\/ \u4fee\u6b63\u53c2\u6570\u8ba1\u6570，\u56e0\u4e3awhile \u5faa\u73af\u4e2d g_argc++ \u5728\u8d4b\u503c\u540e\u6267\u884c\u7684
\n return g_argc > 0 ? true : false;
\n} <\/p>\n（5）\u68c0\u6d4b\u5e76\u6267\u884c\u5185\u952e\u547d\u4ee4<\/h4>\n
\nint lastcode = 0;<\/p>\n
\n#define MAXARGC 128
\nchar *g_argv[MAXARGC];
\nint g_argc = 0;<\/p>\n
\nbool CD()
\n{<\/p>\n
\n {
\n std::string home = GetHome();
\n if(home.empty()) return true;
\n chdir(home.c_str()); \/\/ \u5207\u6362\u8def\u5f84
\n }
\n else
\n {
\n std::string where = g_argv[1]; \/\/ \u76ee\u6807\u8def\u5f84
\n if(where == "-")
\n {}
\n else if(where == "~")
\n {}
\n else
\n {
\n chdir(where.c_str());
\n }
\n }
\n return true;
\n}<\/p>\n
\n{
\n if(g_argc == 2)
\n {
\n \/\/
\n std::string opt = g_argv[1];
\n if(opt == "$?") \/\/ eg1: echo $? \u6253\u5370\u9000\u51fa\u7801
\n {
\n std::cout << lastcode << std::endl;
\n lastcode = 0;
\n return true;
\n }
\n if(opt[0] == '$') \/\/ eg2: echo $PATH \u6253\u5370\u73af\u5883\u53d8\u91cf
\n {
\n std::string env_name = opt.substr(1);
\n const char * env_value = getenv(env_name.c_str()); \/\/ \u83b7\u53d6\u73af\u5883\u53d8\u91cf\u7684\u503c
\n if(env_value)
\n std::cout << env_value << std::endl;
\n }
\n }
\n return false;
\n}<\/p>\n
\nbool CheckAndExecBuiltin()
\n{
\n std::string cmd = g_argv[0];
\n if(cmd == "cd")
\n {
\n return CD();
\n }
\n else if(cmd == "echo")
\n {
\n return Echo();
\n }
\n return false;
\n} <\/p>\n（6）\u6267\u884c\u547d\u4ee4<\/h4>\n
\nint Execute()
\n{
\n pid_t id = fork();
\n if(id == 0)
\n {
\n \/\/ child, \u7a0b\u5e8f\u66ff\u6362
\n execvp(g_argv[0], g_argv);
\n exit(1);
\n }
\n \/\/ father
\n int status = 0;
\n pid_t rid = waitpid(id, &status, 0);
\n if(rid > 0)
\n {
\n lastcode = WEXITSTATUS(status);
\n }
\n return 1;
\n} <\/p>\n（7）\u5b8c\u6574\u4ee3\u7801<\/h4>\n
\n#include<cstdio>
\n#include<cstdlib>
\n#include<cstring>
\n#include<unistd.h>
\n#include<sys\/types.h>
\n#include<sys\/wait.h><\/p>\n
\n#define HOSTNAME_MAX 1024
\n#define FORMAT "[%s@%s:%s]# "<\/p>\n
\n#define MAXARGC 128
\nchar *g_argv[MAXARGC];
\nint g_argc = 0;<\/p>\n
\nchar cwdenv[1024]; <\/p>\n
\n#define MAX_ENVS 1024
\nchar *g_env[MAX_ENVS];
\nint g_envs = 0;<\/p>\n
\nint lastcode = 0;<\/p>\n
\n{
\n const char * name = getenv("USER");
\n return name == NULL ? "None" : name;
\n}<\/p>\n
\n{
\n char hostname[HOSTNAME_MAX];
\n return (gethostname(hostname, HOSTNAME_MAX) == -1) ? "None" : hostname;
\n}<\/p>\n
\n{
\n \/\/const char * pwd = getenv("PWD");
\n const char *pwd = getcwd(cwd, sizeof(cwd)); \/\/ \u901a\u8fc7\u7cfb\u7edf\u8c03\u7528\u83b7\u53d6
\n if(pwd != NULL)
\n { \/\/ \u628a\u81ea\u5df1\u7684\u73af\u5883\u53d8\u91cf\u5bfc\u7ed9\u8fdb\u7a0b
\n snprintf(cwdenv, sizeof(cwdenv), "PWD=%s", cwd);
\n putenv(cwdenv);
\n }
\n return pwd == NULL ? "None" : pwd;
\n}<\/p>\n
\n{
\n const char *home = getenv("HOME");
\n return home == "" ? NULL : home;
\n}<\/p>\n
\nstd::string DirName(const char *pwd)
\n{
\n#define SLASH "\/"
\n std::string dir = pwd;
\n if(dir == SLASH) return SLASH;
\n auto pos = dir.rfind(SLASH);
\n if(pos == std::string::npos) return "BUG";
\n return dir.substr(pos+1);
\n}<\/p>\n
\nvoid MakeCommandline(char cmd_prompt[], int size)
\n{
\n \/\/ \u8bbe\u7f6e\u5f0f\u5316\u8f93\u5165
\n snprintf(cmd_prompt, size, FORMAT, GetUserName(), GetHostName(), DirName(GetPwd()).c_str());
\n \/\/snprintf(cmd_prompt, size, FORMAT, GetUserName(), GetHostName(), GetPwd());
\n}<\/p>\n
\nvoid PrintCommandline()
\n{
\n char prompt[COMMAND_SIZE];
\n MakeCommandline(prompt, COMMAND_SIZE);
\n printf("%s", prompt);
\n fflush(stdout);
\n}<\/p>\n
\nbool GetCommandline(char *out, int size)
\n{
\n \/\/ \u4ece\u6807\u51c6\u8f93\u5165\u6d41\u83b7\u53d6\u547d\u4ee4，\u5176\u5b9e\u5c31\u662f\u5b57\u7b26\u4e32
\n char* c = fgets(out, size, stdin);<\/p>\n
\n out[strlen(out)-1] = '\\\\0'; \/\/ \u6e05\u7406\\\\n, \u81f3\u5c11\u4f1a\u6309\u4e00\u6b21\u56de\u8f66，\u6240\u4ee5\u4e0d\u4f1a\u51fa\u9519<\/p>\n
\n return true;
\n}<\/p>\n
\nbool CommandParse(char *commandline)
\n{
\n \/\/ "ls -a -l" -> "ls" "-a" "-l"
\n \/\/ \u5b57\u7b26\u4e32\u5207\u5272 strtok()\u51fd\u6570
\n#define SEP " "
\n g_argc = 0;
\n \/\/ \u7b2c\u4e00\u6b21\u8c03\u7528：\u4f20\u5165\u8981\u5206\u5272\u7684\u5b57\u7b26\u4e32\u548c\u5206\u9694\u7b26
\n g_argv[g_argc++] = strtok(commandline, SEP);
\n \/\/ \u540e\u7eed\u8c03\u7528：\u4f20\u5165 NULL \u548c\u5206\u9694\u7b26，\u7ee7\u7eed\u5206\u5272\u540c\u4e00\u5b57\u7b26\u4e32
\n while(g_argv[g_argc++] = strtok(NULL, SEP));
\n g_argc–;
\n return g_argc > 0 ? true : false;
\n}<\/p>\n
\n{
\n for(int i = 0; g_argv[i]; i++)
\n {
\n printf("argv[%d]->%s\\\\n", i, g_argv[i]);
\n }
\n printf("%d\\\\n",g_argc);
\n}<\/p>\n
\nvoid InitEnv()
\n{
\n extern char **environ;
\n memset(g_env, 0, sizeof(g_env)); \/\/ \u521d\u59cb\u5316
\n g_envs = 0;<\/p>\n
\n for(int i = 0; environ[i]; i++)
\n {
\n \/\/ (1)\u7533\u8bf7\u7a7a\u95f4
\n g_env[i] = (char*)malloc(strlen(environ[i])+1);
\n \/\/ (2)\u62f7\u8d1d\u5230\u6211\u4eec\u7684\u73af\u5883\u53d8\u91cf\u8868
\n strcpy(g_env[i], environ[i]);
\n g_envs++;
\n }
\n \/\/ \u6d4b\u8bd5：\u6dfb\u52a0\u4e86\u4e00\u4e2a\u65b0\u7684\u73af\u5883\u53d8\u91cf
\n g_env[g_envs++] = (char*)"HAHA=for_test";
\n g_env[g_envs] = NULL; \/\/ \u8868\u7684\u6700\u540e\u4e00\u4e2a\u6210\u5458\u5fc5\u987b\u662fNULL<\/p>\n
\n for(int i = 0; g_env[i]; i++)
\n {
\n putenv(g_env[i]);
\n }
\n}<\/p>\n
\nbool CD()
\n{<\/p>\n
\n {
\n std::string home = GetHome();
\n if(home.empty()) return true;
\n chdir(home.c_str());
\n }
\n else
\n {
\n std::string where = g_argv[1];
\n if(where == "-")
\n {}
\n else if(where == "~")
\n {}
\n else
\n {
\n chdir(where.c_str());
\n }
\n }
\n return true;
\n}<\/p>\n
\n{
\n if(g_argc == 2)
\n {
\n \/\/
\n std::string opt = g_argv[1];
\n if(opt == "$?") \/\/ eg1: echo $?
\n {
\n std::cout << lastcode << std::endl;
\n lastcode = 0;
\n return true;
\n }
\n if(opt[0] == '$') \/\/ eg2: echo $PATH
\n {
\n std::string env_name = opt.substr(1);
\n const char * env_value = getenv(env_name.c_str()); \/\/ \u83b7\u53d6\u73af\u5883\u53d8\u91cf\u7684\u503c
\n if(env_value)
\n std::cout << env_value << std::endl;
\n }
\n }
\n return false;
\n}<\/p>\n
\nbool CheckAndExecBuiltin()
\n{
\n std::string cmd = g_argv[0];
\n if(cmd == "cd")
\n {
\n return CD();
\n }
\n else if(cmd == "echo")
\n {
\n return Echo();
\n }
\n return false;
\n}<\/p>\n
\nint Execute()
\n{
\n pid_t id = fork();
\n if(id == 0)
\n {
\n \/\/ child, \u7a0b\u5e8f\u66ff\u6362
\n execvp(g_argv[0], g_argv);
\n exit(1);
\n }
\n \/\/ father
\n int status = 0;
\n pid_t rid = waitpid(id, &status, 0);
\n if(rid > 0)
\n {
\n lastcode = WEXITSTATUS(status);
\n }
\n return 1;
\n}
\n\/\/ \u91ca\u653e\u901a\u8fc7malloc\u5206\u914d\u7684\u73af\u5883\u53d8\u91cf\u5185\u5b58
\nvoid FreeEnvMemory1()
\n{
\n for(int i = 0; i < g_envs; i++) {
\n if(g_env[i] != NULL) {
\n free(g_env[i]); \/\/ \u91ca\u653e\u6bcf\u4e2a\u73af\u5883\u53d8\u91cf\u5b57\u7b26\u4e32
\n g_env[i] = NULL; \/\/ \u7f6e\u7a7a\u6307\u9488
\n }
\n }
\n g_envs = 0; \/\/ \u91cd\u7f6e\u8ba1\u6570\u5668
\n}<\/p>\n
\n if (!g_used_putenv) {
\n \/\/ \u672a\u8c03\u7528 putenv，\u53ef\u4ee5\u5b89\u5168\u91ca\u653e
\n for (int i = 0; i < g_envs; i++) {
\n free(g_env[i]);
\n g_env[i] = NULL;
\n }
\n } else {
\n \/\/ \u8c03\u7528\u8fc7 putenv，\u53ea\u80fd\u91ca\u653e\u6570\u7ec4\u6307\u9488（\u4e0d\u91ca\u653e\u5b57\u7b26\u4e32\u5185\u5b58）
\n for (int i = 0; i < g_envs; i++) {
\n g_env[i] = NULL; \/\/ \u4ec5\u7f6e\u7a7a\u6307\u9488
\n }
\n }
\n g_envs = 0;
\n}<\/p>\n
\n{
\n \/\/ shell\u542f\u52a8\u8981\u4ece\u7cfb\u7edf\u4e2d\u83b7\u53d6\u73af\u5883\u53d8\u91cf，\u800c\u6211\u4eec\u7684\u73af\u5883\u53d8\u91cf\u4fe1\u606f\u8981\u4ece\u7236shell\u4e2d\u83b7\u53d6
\n InitEnv();
\n \/\/ \u5f53\u7136\u662f\u5faa\u73af\u5566！
\n while(true)
\n {
\n \/\/ 1\u3001\u8f93\u51fa\u547d\u4ee4\u884c\u63d0\u793a\u7b26
\n PrintCommandline();<\/p>\n
\n char commandline[COMMAND_SIZE];
\n if(!GetCommandline(commandline, COMMAND_SIZE))
\n continue;
\n \/\/printf("%s\\\\n", commandline);<\/p>\n
\n if(!CommandParse(commandline)) continue;
\n \/\/PrintArray();<\/p>\n
\n if(CheckAndExecBuiltin()) continue;<\/p>\n
\n Execute();
\n }
\n \/\/ \u91ca\u653e\u7a7a\u95f4
\n FreeEnvMemory();
\n return 0;
\n} <\/p>\n\u00a0\u4e09\u3001\u51fd\u6570\u548c\u8fdb\u7a0b\u4e4b\u95f4\u7684\u76f8\u4f3c\u6027<\/h2>\n
![\"\"](\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/04\/20250426053028-680c6f74409a7.png\")
<\/p>\n