system.c

unix环境高级编程的源代码

#include    <sys/types.h>
#include    <sys/wait.h>
#include    <errno.h>
#include    <unistd.h>

int
system(const char *cmdstring)    /* version without signal handling */
{
    pid_t    pid;
    int        status;

    if (cmdstring == NULL)
        return(1);        /* always a command processor with Unix */

    if ( (pid = fork()) < 0) {
        status = -1;    /* probably out of processes */

    } else if (pid == 0) {                /* child */
        execl("/bin/sh", "sh", "-c", cmdstring, (char *) 0);
        _exit(127);        /* execl error */

    } else {                            /* parent */
        while (waitpid(pid, &status, 0) < 0)
            if (errno != EINTR) {
                status = -1; /* error other than EINTR from waitpid() */
                break;
            }
    }

    return(status);
}