1 | /* $NetBSD: popen.c,v 1.11 1995/06/16 07:05:33 jtc Exp $ */ |
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2 | |
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3 | /* |
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4 | * Copyright (c) 1988, 1993, 2006 |
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5 | * The Regents of the University of California. All rights reserved. |
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6 | * |
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7 | * This code is derived from software written by Ken Arnold and |
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8 | * published in UNIX Review, Vol. 6, No. 8. |
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9 | * |
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10 | * Redistribution and use in source and binary forms, with or without |
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11 | * modification, are permitted provided that the following conditions |
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12 | * are met: |
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13 | * 1. Redistributions of source code must retain the above copyright |
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14 | * notice, this list of conditions and the following disclaimer. |
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15 | * 2. Redistributions in binary form must reproduce the above copyright |
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16 | * notice, this list of conditions and the following disclaimer in the |
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17 | * documentation and/or other materials provided with the distribution. |
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18 | * 4. Neither the name of the University nor the names of its contributors |
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19 | * may be used to endorse or promote products derived from this software |
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20 | * without specific prior written permission. |
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21 | * |
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22 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
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23 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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24 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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25 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
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26 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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27 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
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28 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
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29 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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30 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
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31 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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32 | * SUCH DAMAGE. |
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33 | */ |
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34 | |
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35 | /* |
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36 | FUNCTION |
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37 | <<popen>>, <<pclose>>---tie a stream to a command string |
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38 | |
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39 | INDEX |
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40 | popen |
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41 | INDEX |
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42 | pclose |
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43 | |
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44 | SYNOPSIS |
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45 | #include <stdio.h> |
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46 | FILE *popen(const char *<[s]>, const char *<[mode]>); |
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47 | |
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48 | int pclose(FILE *<[f]>); |
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49 | |
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50 | DESCRIPTION |
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51 | Use <<popen>> to create a stream to a child process executing a |
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52 | command string <<*<[s]>>> as processed by <</bin/sh>> on your system. |
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53 | The argument <[mode]> must start with either `<<r>>', where the stream |
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54 | reads from the child's <<stdout>>, or `<<w>>', where the stream writes |
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55 | to the child's <<stdin>>. As an extension, <[mode]> may also contain |
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56 | `<<e>>' to set the close-on-exec bit of the parent's file descriptor. |
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57 | The stream created by <<popen>> must be closed by <<pclose>> to avoid |
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58 | resource leaks. |
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59 | |
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60 | Streams created by prior calls to <<popen>> are not visible in |
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61 | subsequent <<popen>> children, regardless of the close-on-exec bit. |
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62 | |
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63 | Use ``<<system(NULL)>>'' to test whether your system has <</bin/sh>> |
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64 | available. |
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65 | |
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66 | RETURNS |
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67 | <<popen>> returns a file stream opened with the specified <[mode]>, |
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68 | or <<NULL>> if a child process could not be created. <<pclose>> |
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69 | returns -1 if the stream was not created by <<popen>> or if the |
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70 | application used <<wait>> or similar to steal the status; otherwise |
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71 | it returns the exit status of the child which can be interpreted |
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72 | in the same manner as a status obtained by <<waitpid>>. |
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73 | |
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74 | PORTABILITY |
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75 | POSIX.2 requires <<popen>> and <<pclose>>, but only specifies a mode |
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76 | of just <<r>> or <<w>>. Where <<sh>> is found is left unspecified. |
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77 | |
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78 | Supporting OS subroutines required: <<_exit>>, <<_execve>>, <<_fork_r>>, |
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79 | <<_wait_r>>, <<pipe>>, <<fcntl>>, <<sbrk>>. |
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80 | */ |
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81 | |
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82 | #ifndef _NO_POPEN |
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83 | |
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84 | #if defined(LIBC_SCCS) && !defined(lint) |
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85 | #if 0 |
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86 | static char sccsid[] = "@(#)popen.c 8.1 (Berkeley) 6/4/93"; |
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87 | #else |
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88 | static char rcsid[] = "$NetBSD: popen.c,v 1.11 1995/06/16 07:05:33 jtc Exp $"; |
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89 | #endif |
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90 | #endif /* LIBC_SCCS and not lint */ |
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91 | |
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92 | #include <sys/param.h> |
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93 | #include <sys/types.h> |
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94 | #include <sys/wait.h> |
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95 | |
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96 | #include <signal.h> |
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97 | #include <errno.h> |
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98 | #include <unistd.h> |
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99 | #include <stdio.h> |
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100 | #include <stdlib.h> |
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101 | #include <string.h> |
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102 | #include <paths.h> |
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103 | #include <fcntl.h> |
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104 | |
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105 | static struct pid { |
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106 | struct pid *next; |
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107 | FILE *fp; |
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108 | pid_t pid; |
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109 | } *pidlist; |
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110 | |
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111 | FILE * |
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112 | popen (const char *program, |
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113 | const char *type) |
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114 | { |
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115 | struct pid *cur; |
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116 | FILE *iop; |
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117 | int pdes[2], pid; |
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118 | |
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119 | if ((*type != 'r' && *type != 'w') |
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120 | || (type[1] |
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121 | #ifdef HAVE_FCNTL |
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122 | && (type[2] || (type[1] != 'e')) |
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123 | #endif |
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124 | )) { |
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125 | errno = EINVAL; |
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126 | return (NULL); |
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127 | } |
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128 | |
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129 | if ((cur = malloc(sizeof(struct pid))) == NULL) |
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130 | return (NULL); |
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131 | |
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132 | if (pipe(pdes) < 0) { |
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133 | free(cur); |
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134 | return (NULL); |
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135 | } |
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136 | |
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137 | switch (pid = vfork()) { |
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138 | case -1: /* Error. */ |
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139 | (void)close(pdes[0]); |
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140 | (void)close(pdes[1]); |
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141 | free(cur); |
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142 | return (NULL); |
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143 | /* NOTREACHED */ |
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144 | case 0: /* Child. */ |
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145 | if (*type == 'r') { |
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146 | if (pdes[1] != STDOUT_FILENO) { |
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147 | (void)dup2(pdes[1], STDOUT_FILENO); |
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148 | (void)close(pdes[1]); |
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149 | } |
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150 | if (pdes[0] != STDOUT_FILENO) { |
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151 | (void) close(pdes[0]); |
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152 | } |
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153 | } else { |
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154 | if (pdes[0] != STDIN_FILENO) { |
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155 | (void)dup2(pdes[0], STDIN_FILENO); |
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156 | (void)close(pdes[0]); |
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157 | } |
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158 | (void)close(pdes[1]); |
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159 | } |
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160 | /* Close all fd's created by prior popen. */ |
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161 | for (cur = pidlist; cur; cur = cur->next) |
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162 | (void)close (fileno (cur->fp)); |
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163 | execl(_PATH_BSHELL, "sh", "-c", program, NULL); |
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164 | _exit(127); |
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165 | /* NOTREACHED */ |
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166 | } |
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167 | |
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168 | /* Parent; assume fdopen can't fail. */ |
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169 | if (*type == 'r') { |
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170 | iop = fdopen(pdes[0], type); |
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171 | (void)close(pdes[1]); |
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172 | } else { |
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173 | iop = fdopen(pdes[1], type); |
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174 | (void)close(pdes[0]); |
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175 | } |
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176 | |
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177 | #ifdef HAVE_FCNTL |
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178 | /* Mark pipe cloexec if requested. */ |
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179 | if (type[1] == 'e') |
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180 | fcntl (fileno (iop), F_SETFD, |
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181 | fcntl (fileno (iop), F_GETFD, 0) | FD_CLOEXEC); |
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182 | #endif /* HAVE_FCNTL */ |
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183 | |
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184 | /* Link into list of file descriptors. */ |
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185 | cur->fp = iop; |
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186 | cur->pid = pid; |
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187 | cur->next = pidlist; |
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188 | pidlist = cur; |
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189 | |
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190 | return (iop); |
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191 | } |
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192 | |
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193 | /* |
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194 | * pclose -- |
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195 | * Pclose returns -1 if stream is not associated with a `popened' command, |
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196 | * if already `pclosed', or waitpid returns an error. |
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197 | */ |
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198 | int |
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199 | pclose (FILE *iop) |
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200 | { |
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201 | register struct pid *cur, *last; |
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202 | int pstat; |
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203 | pid_t pid; |
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204 | |
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205 | (void)fclose(iop); |
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206 | |
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207 | /* Find the appropriate file pointer. */ |
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208 | for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next) |
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209 | if (cur->fp == iop) |
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210 | break; |
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211 | if (cur == NULL) |
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212 | return (-1); |
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213 | |
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214 | do { |
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215 | pid = waitpid(cur->pid, &pstat, 0); |
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216 | } while (pid == -1 && errno == EINTR); |
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217 | |
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218 | /* Remove the entry from the linked list. */ |
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219 | if (last == NULL) |
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220 | pidlist = cur->next; |
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221 | else |
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222 | last->next = cur->next; |
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223 | free(cur); |
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224 | |
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225 | return (pid == -1 ? -1 : pstat); |
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226 | } |
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227 | |
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228 | #endif /* !_NO_POPEN */ |
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