popen.c revision 25063
1/* 2 * Copyright (c) 1988, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software written by Ken Arnold and 6 * published in UNIX Review, Vol. 6, No. 8. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37#if defined(LIBC_SCCS) && !defined(lint) 38static char sccsid[] = "@(#)popen.c 8.3 (Berkeley) 5/3/95"; 39#endif /* LIBC_SCCS and not lint */ 40 41#include <sys/param.h> 42#include <sys/wait.h> 43 44#include <signal.h> 45#include <errno.h> 46#include <unistd.h> 47#include <stdio.h> 48#include <stdlib.h> 49#include <string.h> 50#include <paths.h> 51 52static struct pid { 53 struct pid *next; 54 FILE *fp; 55 pid_t pid; 56} *pidlist; 57 58FILE * 59popen(command, type) 60 const char *command, *type; 61{ 62 struct pid *cur; 63 FILE *iop; 64 int pdes[2], pid, twoway; 65 66 /* 67 * Lite2 introduced two-way popen() pipes using socketpair(). 68 * FreeBSD's pipe() is bidirectional, so we use that. 69 */ 70 if (strchr(type, '+')) { 71 twoway = 1; 72 type = "r+"; 73 } else { 74 twoway = 0; 75 if ((*type != 'r' && *type != 'w') || type[1]) 76 return (NULL); 77 } 78 if (pipe(pdes) < 0) 79 return (NULL); 80 81 if ((cur = malloc(sizeof(struct pid))) == NULL) { 82 (void)close(pdes[0]); 83 (void)close(pdes[1]); 84 return (NULL); 85 } 86 87 switch (pid = vfork()) { 88 case -1: /* Error. */ 89 (void)close(pdes[0]); 90 (void)close(pdes[1]); 91 free(cur); 92 return (NULL); 93 /* NOTREACHED */ 94 case 0: /* Child. */ 95 if (*type == 'r') { 96 /* 97 * The dup2() to STDIN_FILENO is repeated to avoid 98 * writing to pdes[1], which might corrupt the 99 * parent's copy. This isn't good enough in 100 * general, since the _exit() is no return, so 101 * the compiler is free to corrupt all the local 102 * variables. 103 */ 104 (void) close(pdes[0]); 105 if (pdes[1] != STDOUT_FILENO) { 106 (void)dup2(pdes[1], STDOUT_FILENO); 107 (void)close(pdes[1]); 108 (void)dup2(STDOUT_FILENO, STDIN_FILENO); 109 } else if (twoway && (pdes[1] != STDIN_FILENO)) 110 (void)dup2(pdes[1], STDIN_FILENO); 111 } else { 112 if (pdes[0] != STDIN_FILENO) { 113 (void)dup2(pdes[0], STDIN_FILENO); 114 (void)close(pdes[0]); 115 } 116 (void)close(pdes[1]); 117 } 118 execl(_PATH_BSHELL, "sh", "-c", command, NULL); 119 _exit(127); 120 /* NOTREACHED */ 121 } 122 123 /* Parent; assume fdopen can't fail. */ 124 if (*type == 'r') { 125 iop = fdopen(pdes[0], type); 126 (void)close(pdes[1]); 127 } else { 128 iop = fdopen(pdes[1], type); 129 (void)close(pdes[0]); 130 } 131 132 /* Link into list of file descriptors. */ 133 cur->fp = iop; 134 cur->pid = pid; 135 cur->next = pidlist; 136 pidlist = cur; 137 138 return (iop); 139} 140 141/* 142 * pclose -- 143 * Pclose returns -1 if stream is not associated with a `popened' command, 144 * if already `pclosed', or waitpid returns an error. 145 */ 146int 147pclose(iop) 148 FILE *iop; 149{ 150 register struct pid *cur, *last; 151 int omask; 152 int pstat; 153 pid_t pid; 154 155 /* Find the appropriate file pointer. */ 156 for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next) 157 if (cur->fp == iop) 158 break; 159 if (cur == NULL) 160 return (-1); 161 162 (void)fclose(iop); 163 164 do { 165 pid = waitpid(cur->pid, &pstat, 0); 166 } while (pid == -1 && errno == EINTR); 167 168 /* Remove the entry from the linked list. */ 169 if (last == NULL) 170 pidlist = cur->next; 171 else 172 last->next = cur->next; 173 free(cur); 174 175 return (pid == -1 ? -1 : pstat); 176} 177