system执行shell命令

system - execute a shell command

#include <stdlib.h>

int system (const char *command);

描述

system() executes a command specified in command by calling /bin/sh -c command, and returns after the command has been completed. During excution of the comman, SIGCHLD will be bocked, and SIGINT and SIGQUIT will be ignored.

返回值

错误返回-1，成功返回命令的退出状态。退出状态格式由wait指定，因此，命令的退出码是WEXITSTATUS(status). In case /bin/sh could not be executed, the exit status will be that of a command that dose exit(127).

If the value of command is NULL, system() returns nonzero if the shell is available, and zero if not.

system() does not affect the wait status of any other children.

注意

As mentioned, system() ignores SIGINT and SIGQUIT. This may make programs that call it from a loop uniterruptible, unless they take care themselves to check the exit status of the childl. E.g.

　　while(something) {

　　　　int ret = system("foo");

　　　　if(WIFSIGNALED(ret) && (WTERMSIG(ret) == SIGINT || WTERMSIG(ret) == SIGQUIT))

　　　　　　break;

　　}

It is possible for the shell command to return 127, so that code is not a sure indication that the execve call fialed.