用c语言实现的shell解释器

#include <errno.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/wait.h> #include <unistd.h> #define MAX_HOST_LEN 32 /* 主机名最大长度 */ #define MAX_PATH_LEN 256 /* 路径的最大长度 */ #define MAX_COMMAND_LEN 256 /*命令的最大长度*/ struct job { char * precmd; /* 转换前的命令*/ char ** formatcmd; /* 转换后的命令*/ }; struct promptinfo { char * username; /* 当前用户名*/ char * hostname; /* 主机名*/ uid_t userid; /* 当前用户id */ char * pwdname; /* 当前路径名 */ char promptchar; /* '#' 为管理员, '$' 普通用户 */ char * home; /* 主路径 */ }prinfo; int getprinfo() { prinfo.userid = getuid();/*得到用户ID*/ /* 得到当前用户名 */ if ( (prinfo.username = getenv("USER")) == NULL) { perror("getlogin error"); return -1; } /* 获得主机名*/ if ( (prinfo.hostname = malloc(MAX_HOST_LEN) ) == NULL) { perror("malloc hostname error"); return -2; } if ( gethostname(prinfo.hostname, MAX_HOST_LEN) != 0) { perror("get hostname error"); return -2; } /* 获得当前路径名*/ if ( (prinfo.pwdname = malloc(MAX_PATH_LEN) ) == NULL) { perror("malloc pwdname error"); return -3; } if ( (prinfo.pwdname = getcwd(prinfo.pwdname, MAX_PATH_LEN)) == NULL) { perror("get current path error"); return -3; } /* 获得命令行提示符 */ if (prinfo.userid < 0) { printf("getuid error."); return -4; } if (prinfo.userid == 0) { prinfo.promptchar = '#'; } else { prinfo.promptchar = '$'; } /* 获得主路径名*/ if ( (prinfo.home = getenv("HOME")) == NULL) { perror("get home path error"); return -5; } return 0; } void prompt() { printf("\033[00;32m%s\033[00;35m@\033[00;36m%s\033[00;33m:\033[00;34m%s\033[00;31m%c\033[00m ", prinfo.username, prinfo.hostname, prinfo.pwdname, prinfo.promptchar); } char ** parseCommand(char * precommand, char ** formatcmd) { /*把命令转换成字符串数组 */ char c; int count = 0,i = 0,j = 0; if ( (formatcmd = malloc(sizeof(char*))) == NULL) { perror("malloc to formatcmd error"); return NULL; } if ( (formatcmd[0] = malloc( (strlen(precommand) + 1) * (sizeof(char) ) ) ) == NULL) { perror("malloc to formatcmd[0] error"); return NULL; } while ((c = precommand[i]) == 32) { i++; } /* 忽略命令前面的空格*/ while (i < strlen(precommand)) { c = precommand[i]; if (c == 32) { while ((c = precommand[i]) == 32) { i++; } formatcmd[count][j] = '\0'; count++; formatcmd = realloc(formatcmd, count); if ( (formatcmd[count] = malloc(sizeof(char) * (strlen(precommand) - i + 1) )) == NULL) { fprintf(stderr, "malloc formatcmd[%d] error %d: %s", count, errno, strerror(errno)); return NULL; } j = 0; } else { formatcmd[count][j] = c; j++; i++; } } formatcmd[count][j] = '\0'; count++; formatcmd = realloc(formatcmd, count); formatcmd[count] = NULL; return formatcmd; } /* main fuction here !!! */ int main(int argc, char * argv[]) { struct job joba; char cmdbuf[MAX_COMMAND_LEN]; pid_t child; int status; if (getprinfo() < 0) { printf("getprinfo error\n"); exit(-1); } prompt(); while ((fgets(cmdbuf, MAX_COMMAND_LEN, stdin)) != NULL) { cmdbuf[strlen(cmdbuf) -1] = '\0';/* 以‘\0'结束*/ if (strcmp(cmdbuf, "exit") ==0) { exit(0); } joba.precmd = cmdbuf; if ((joba.formatcmd = parseCommand(joba.precmd, joba.formatcmd)) != NULL) { /*如果只输入cd不带参数 直接进入主目录 */ if (strcmp(joba.formatcmd[0], "cd") == 0) { if (joba.formatcmd[1] == NULL){ joba.formatcmd[1] = prinfo.home; } if (chdir(joba.formatcmd[1]) < 0) { perror("cd"); } getprinfo(); } else { if ((child = fork()) < 0) { /* 创建子进程失败 */ fprintf(stderr, "fork error %d: %s\n", errno, strerror(errno)); } /* 进入子进程 */ if(child == 0) { if (execvp(joba.formatcmd[0], joba.formatcmd) < 0){ perror("exec error"); } exit(0); } /* 等待子进程结束 */ if ((waitpid(child, &status, 0)) < 0) { perror("waitpid error"); } } } prompt(); } return 0; }