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#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <spawn.h>
#include "stdio_impl.h"
#include "syscall.h"
extern char **__environ;
FILE *popen(const char *cmd, const char *mode)
{
int p[2], op, e;
pid_t pid;
FILE *f;
posix_spawn_file_actions_t fa;
if (*mode == 'r') {
op = 0;
} else if (*mode == 'w') {
op = 1;
} else {
errno = EINVAL;
return 0;
}
if (pipe2(p, O_CLOEXEC)) return NULL;
f = fdopen(p[op], mode);
if (!f) {
__syscall(SYS_close, p[0]);
__syscall(SYS_close, p[1]);
return NULL;
}
FLOCK(f);
/* If the child's end of the pipe happens to already be on the final
* fd number to which it will be assigned (either 0 or 1), it must
* be moved to a different fd. Otherwise, there is no safe way to
* remove the close-on-exec flag in the child without also creating
* a file descriptor leak race condition in the parent. */
if (p[1-op] == 1-op) {
int tmp = fcntl(1-op, F_DUPFD_CLOEXEC, 0);
if (tmp < 0) {
e = errno;
goto fail;
}
__syscall(SYS_close, p[1-op]);
p[1-op] = tmp;
}
e = ENOMEM;
if (!posix_spawn_file_actions_init(&fa)) {
if (!posix_spawn_file_actions_adddup2(&fa, p[1-op], 1-op)) {
if (!(e = posix_spawn(&pid, "/bin/sh", &fa, 0,
(char *[]){ "sh", "-c", (char *)cmd, 0 }, __environ))) {
posix_spawn_file_actions_destroy(&fa);
f->pipe_pid = pid;
if (!strchr(mode, 'e'))
fcntl(p[op], F_SETFD, 0);
__syscall(SYS_close, p[1-op]);
FUNLOCK(f);
return f;
}
}
posix_spawn_file_actions_destroy(&fa);
}
fail:
fclose(f);
__syscall(SYS_close, p[1-op]);
errno = e;
return 0;
}
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