用標准C實現shell功能

　　#include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <sys/wait.h> #include <string.h> #include <errno.h> #define SHELL_NAME "sh1" #define PROMPT_ENVIRONMENT_VARIABLE "PROMPT" char *prompt; int main(int argc, char **argv) { char cmd[80]; int statval; /* Determine prompt value. */ if ((prompt = getenv(PROMPT_ENVIRONMENT_VARIABLE)) == NULL) prompt = SHELL_NAME ":"; /* Process commands until exit, or death by signal. */ while (1) { /* Prompt and read a command. */ printf(prompt); gets(cmd); /* Process built-in commands. */ if(strcasecmp(cmd, "exit") == 0) break; /* Process non-built-in commands. */ if(fork() == 0) { execlp(cmd, cmd, NULL); fprintf(stderr, "%s: Exec %s failed: %s\n", argv[0], cmd, strerror(errno)); exit(1); } wait(&statval); if(WIFEXITED(statval)) { if(WEXITSTATUS(statval)) { fprintf(stderr, "%s: child exited with status %d.\n", argv[0], WEXITSTATUS(statval)); } } else { fprintf(stderr, "%s: child died uneXPectedly.\n", argv[0]); } } }