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#include <stdlib.h>
#if defined _POSIX_SOURCE || defined _POSIX_C_SOURCE || defined _XOPEN_SOURCE
# include "errno.h"
# include "sys/types.h"
# include "unistd.h"
# include "sys/wait.h"
# define USE_FORK
#endif
/** execute a command **/
int system(const char * string)
{
#if defined USE_FORK
pid_t pid;
int status;
if (string == NULL) {
return 0;
}
/* ignore SIGINT and SIGQUIT */
/* block SIGCHLD */
pid = fork();
if (pid < 0) {
/* errno comes from fork() */
return -1;
}
if (pid == 0) {
/* restore signal handlers */
execl("/bin/sh", "sh", "-c", string, (char *)0);
_exit(127);
}
if (waitpid(pid, &status, 0) == -1) {
errno = ECHILD;
status = -1;
}
/* restore signal handlers */
if (WIFSIGNALED(status)) {
}
return status;
#else
(void)string;
return 1;
#endif
}
/***
runs the command ARGUMENT(string) using the host environment's command
processor.
Specifying CONSTANT(NULL) for ARGUMENT(string) tests whether a command
processor is available.
***/
/*
IMPLEMENTATION(How the command processor is invoked)
IMPLEMENTATION(The return value when ARGUMENT(string) is not CONSTANT(NULL))
RETURN(NONZERO, If ARGUMENT(string) is CONSTANT(NULL), a command processor is available)
RETURN(0, If ARGUMENT(string) is CONSTANT(NULL), a command processor is not available)
STDC(1)
*/
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