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/* Copyright (C) 2004 Manuel Novoa III <mjn3@codepoet.org>
*
* GNU Library General Public License (LGPL) version 2 or later.
*
* Dedicated to Toni. See uClibc/DEDICATION.mjn3 for details.
*/
/* Jan 1, 2004
*
* Rewrite popen for SUSv3 compliance.
* Added a list of popen()'d to store pids and use waitpid() in pclose().
* Loop on waitpid() failure due to EINTR as required.
* Close parent's popen()'d FILEs in the {v}fork()'d child.
* Fix failure exit code for failed execve().
*/
#define waitpid __waitpid
#define execl __execl
#define dup2 __dup2
#define fdopen __fdopen
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <sys/wait.h>
/* uClinux-2.0 has vfork, but Linux 2.0 doesn't */
#include <sys/syscall.h>
#if ! defined __NR_vfork
# define vfork fork
# define VFORK_LOCK ((void) 0)
# define VFORK_UNLOCK ((void) 0)
#endif
#ifdef __UCLIBC_HAS_THREADS__
# include <pthread.h>
static pthread_mutex_t mylock = PTHREAD_MUTEX_INITIALIZER;
#endif
#define LOCK __pthread_mutex_lock(&mylock)
#define UNLOCK __pthread_mutex_unlock(&mylock)
#ifndef VFORK_LOCK
# define VFORK_LOCK LOCK
# define VFORK_UNLOCK UNLOCK
#endif
struct popen_list_item {
struct popen_list_item *next;
FILE *f;
pid_t pid;
};
static struct popen_list_item *popen_list /* = NULL (bss initialized) */;
FILE *popen(const char *command, const char *modes)
{
FILE *fp;
struct popen_list_item *pi;
struct popen_list_item *po;
int pipe_fd[2];
int parent_fd;
int child_fd;
int child_writing; /* Doubles as the desired child fildes. */
pid_t pid;
child_writing = 0; /* Assume child is writing. */
if (modes[0] != 'w') { /* Parent not writing... */
++child_writing; /* so child must be writing. */
if (modes[0] != 'r') { /* Oops! Parent not reading either! */
__set_errno(EINVAL);
goto RET_NULL;
}
}
if (!(pi = malloc(sizeof(struct popen_list_item)))) {
goto RET_NULL;
}
if (pipe(pipe_fd)) {
goto FREE_PI;
}
child_fd = pipe_fd[child_writing];
parent_fd = pipe_fd[1-child_writing];
if (!(fp = fdopen(parent_fd, modes))) {
__close(parent_fd);
__close(child_fd);
goto FREE_PI;
}
VFORK_LOCK;
if ((pid = vfork()) == 0) { /* Child of vfork... */
__close(parent_fd);
if (child_fd != child_writing) {
dup2(child_fd, child_writing);
__close(child_fd);
}
/* SUSv3 requires that any previously popen()'d streams in the
* parent shall be closed in the child. */
for (po = popen_list ; po ; po = po->next) {
__close(po->f->__filedes);
}
execl("/bin/sh", "sh", "-c", command, (char *)0);
/* SUSv3 mandates an exit code of 127 for the child if the
* command interpreter can not be invoked. */
_exit(127);
}
VFORK_UNLOCK;
/* We need to close the child filedes whether vfork failed or
* it succeeded and we're in the parent. */
__close(child_fd);
if (pid > 0) { /* Parent of vfork... */
pi->pid = pid;
pi->f = fp;
LOCK;
pi->next = popen_list;
popen_list = pi;
UNLOCK;
return fp;
}
/* If we get here, vfork failed. */
fclose(fp); /* Will close parent_fd. */
FREE_PI:
free(pi);
RET_NULL:
return NULL;
}
int pclose(FILE *stream)
{
struct popen_list_item *p;
int stat;
pid_t pid;
/* First, find the list entry corresponding to stream and remove it
* from the list. Set p to the list item (NULL if not found). */
LOCK;
if ((p = popen_list) != NULL) {
if (p->f == stream) {
popen_list = p->next;
} else {
struct popen_list_item *t;
do {
t = p;
if (!(p = t->next)) {
__set_errno(EINVAL); /* Not required by SUSv3. */
break;
}
if (p->f == stream) {
t->next = p->next;
break;
}
} while (1);
}
}
UNLOCK;
if (p) {
pid = p->pid; /* Save the pid we need */
free(p); /* and free the list item. */
fclose(stream); /* The SUSv3 example code ignores the return. */
/* SUSv3 specificly requires that pclose not return before the child
* terminates, in order to disallow pclose from returning on EINTR. */
do {
if (waitpid(pid, &stat, 0) >= 0) {
return stat;
}
if (errno != EINTR) {
break;
}
} while (1);
}
return -1;
}
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