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      1 /*	$OpenBSD: popen.c,v 1.17 2005/08/08 08:05:34 espie Exp $ */
      2 /*
      3  * Copyright (c) 1988, 1993
      4  *	The Regents of the University of California.  All rights reserved.
      5  *
      6  * This code is derived from software written by Ken Arnold and
      7  * published in UNIX Review, Vol. 6, No. 8.
      8  *
      9  * Redistribution and use in source and binary forms, with or without
     10  * modification, are permitted provided that the following conditions
     11  * are met:
     12  * 1. Redistributions of source code must retain the above copyright
     13  *    notice, this list of conditions and the following disclaimer.
     14  * 2. Redistributions in binary form must reproduce the above copyright
     15  *    notice, this list of conditions and the following disclaimer in the
     16  *    documentation and/or other materials provided with the distribution.
     17  * 3. Neither the name of the University nor the names of its contributors
     18  *    may be used to endorse or promote products derived from this software
     19  *    without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     31  * SUCH DAMAGE.
     32  */
     33 
     34 #include <sys/param.h>
     35 #include <sys/wait.h>
     36 
     37 #include <signal.h>
     38 #include <errno.h>
     39 #include <unistd.h>
     40 #include <stdio.h>
     41 #include <stdlib.h>
     42 #include <string.h>
     43 #include <paths.h>
     44 
     45 static struct pid {
     46 	struct pid *next;
     47 	FILE *fp;
     48 	pid_t pid;
     49 } *pidlist;
     50 
     51 extern char **environ;
     52 
     53 FILE *
     54 popen(const char *program, const char *type)
     55 {
     56 	struct pid * volatile cur;
     57 	FILE *iop;
     58 	int pdes[2];
     59 	pid_t pid;
     60 	char *argp[] = {"sh", "-c", NULL, NULL};
     61 
     62 	if ((*type != 'r' && *type != 'w') || type[1] != '\0') {
     63 		errno = EINVAL;
     64 		return (NULL);
     65 	}
     66 
     67 	if ((cur = malloc(sizeof(struct pid))) == NULL)
     68 		return (NULL);
     69 
     70 	if (pipe(pdes) < 0) {
     71 		free(cur);
     72 		return (NULL);
     73 	}
     74 
     75 	switch (pid = fork()) {
     76 	case -1:			/* Error. */
     77 		(void)close(pdes[0]);
     78 		(void)close(pdes[1]);
     79 		free(cur);
     80 		return (NULL);
     81 		/* NOTREACHED */
     82 	case 0:				/* Child. */
     83 	    {
     84 		struct pid *pcur;
     85 		/*
     86 		 * We fork()'d, we got our own copy of the list, no
     87 		 * contention.
     88 		 */
     89 		for (pcur = pidlist; pcur; pcur = pcur->next)
     90 			close(fileno(pcur->fp));
     91 
     92 		if (*type == 'r') {
     93 			(void) close(pdes[0]);
     94 			if (pdes[1] != STDOUT_FILENO) {
     95 				(void)dup2(pdes[1], STDOUT_FILENO);
     96 				(void)close(pdes[1]);
     97 			}
     98 		} else {
     99 			(void)close(pdes[1]);
    100 			if (pdes[0] != STDIN_FILENO) {
    101 				(void)dup2(pdes[0], STDIN_FILENO);
    102 				(void)close(pdes[0]);
    103 			}
    104 		}
    105 		argp[2] = (char *)program;
    106 		execve(_PATH_BSHELL, argp, environ);
    107 		_exit(127);
    108 		/* NOTREACHED */
    109 	    }
    110 	}
    111 
    112 	/* Parent; assume fdopen can't fail. */
    113 	if (*type == 'r') {
    114 		iop = fdopen(pdes[0], type);
    115 		(void)close(pdes[1]);
    116 	} else {
    117 		iop = fdopen(pdes[1], type);
    118 		(void)close(pdes[0]);
    119 	}
    120 
    121 	/* Link into list of file descriptors. */
    122 	cur->fp = iop;
    123 	cur->pid =  pid;
    124 	cur->next = pidlist;
    125 	pidlist = cur;
    126 
    127 	return (iop);
    128 }
    129 
    130 /*
    131  * pclose --
    132  *	Pclose returns -1 if stream is not associated with a `popened' command,
    133  *	if already `pclosed', or waitpid returns an error.
    134  */
    135 int
    136 pclose(FILE *iop)
    137 {
    138 	struct pid *cur, *last;
    139 	int pstat;
    140 	pid_t pid;
    141 
    142 	/* Find the appropriate file pointer. */
    143 	for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
    144 		if (cur->fp == iop)
    145 			break;
    146 
    147 	if (cur == NULL)
    148 		return (-1);
    149 
    150 	(void)fclose(iop);
    151 
    152 	do {
    153 		pid = waitpid(cur->pid, &pstat, 0);
    154 	} while (pid == -1 && errno == EINTR);
    155 
    156 	/* Remove the entry from the linked list. */
    157 	if (last == NULL)
    158 		pidlist = cur->next;
    159 	else
    160 		last->next = cur->next;
    161 	free(cur);
    162 
    163 	return (pid == -1 ? -1 : pstat);
    164 }
    165