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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 4973 | right-hear | 1 | /* Copyright (C) 1995 DJ Delorie, see COPYING.DJ for details */ |
| 2 | /* |
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| 3 | This is popen() and pclose() for MSDOS. They were developed using |
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| 4 | Microsoft C, but should port easily to DOS C any compiler. |
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| 5 | |||
| 6 | Original author: pacetti@fl-ngnet.army.mil |
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| 7 | |||
| 8 | These routines are hacks, that is they SIMULATE thier UNIX |
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| 9 | counterparts. Since MSDOS and won't allow concurrent process spawning, |
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| 10 | you can't really pipe. I came up with this nearly stupid way around |
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| 11 | piping because I wanted to have some portability between UNIX and MSDOS. |
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| 12 | I'm probably not the first person to have this idea or implement it, but |
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| 13 | I think I'm the first to give it away for free (no points?!). |
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| 14 | |||
| 15 | The functions simulate popen() and pclose() by redirecting stdin or |
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| 16 | stdout, then spawning a child processes via system(). |
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| 17 | |||
| 18 | If you popen() for read, the stdout is redirected to a temporary |
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| 19 | file, and the child is spawned. The stdout is reopened via dup2(), the |
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| 20 | temporary file is opened for read and a file pointer to it is returned. |
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| 21 | |||
| 22 | If you popen() for write, a temporary file is opened for write, and |
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| 23 | a file pointer to it is returned. When you pclose(), the stdin is |
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| 24 | redirected to the temporary file and the child is spawned. |
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| 25 | |||
| 26 | In both cases, pclose() closes and unlinks the temporary file. |
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| 27 | |||
| 28 | A static linked list of C structures is built to store necessary |
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| 29 | info for all popen()ed files so you can popen() more than one file at |
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| 30 | a time. |
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| 31 | |||
| 32 | The popen() function will return NULL on an error, or a valid FILE |
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| 33 | *pointer on a successful open. The pclose() function will return |
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| 34 | negative one (-1) on an error or zero (0) on a successful close. |
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| 35 | |||
| 36 | The function prototypes are: |
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| 37 | |||
| 38 | FILE *popen(command, mode) |
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| 39 | char *command, char *mode; |
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| 40 | |||
| 41 | int pclose(pp) |
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| 42 | FILE *pp; |
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| 43 | |||
| 44 | Where command is a character string equivilant to a MSDOS command |
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| 45 | line, mode is "r" for read or "w" for write, and pp is a pointer to a |
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| 46 | file opened through popen(). |
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| 47 | |||
| 48 | A main() function has been included for testing purposes, to compile |
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| 49 | it define the preprocessor token TEST at compile time. |
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| 50 | */ |
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| 51 | |||
| 52 | #include |
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| 53 | #include |
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| 54 | #include |
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| 55 | #include |
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| 56 | #include |
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| 57 | #include |
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| 58 | #include |
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| 59 | #include |
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| 60 | |||
| 61 | /* hold file pointer, descriptor, command, mode, temporary file name */ |
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| 62 | struct pipe_list { |
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| 63 | FILE *fp; |
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| 64 | int fd; |
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| 65 | char *command, mode[10], temp_name[FILENAME_MAX]; |
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| 66 | struct pipe_list *next; |
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| 67 | }; |
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| 68 | |||
| 69 | /* static, global list pointer */ |
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| 70 | static struct pipe_list *pl = NULL; |
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| 71 | |||
| 72 | FILE * |
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| 73 | popen (const char *cm, const char *md) /* program name, pipe mode */ |
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| 74 | { |
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| 75 | struct pipe_list *l1, *l2; |
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| 76 | static char *tn = NULL; /* temporary file basename */ |
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| 77 | |||
| 78 | if (!tn) |
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| 79 | if ((tn = tmpnam(0)) == NULL) |
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| 80 | return NULL; |
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| 81 | |||
| 82 | /* make new node */ |
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| 83 | if ((l1 = (struct pipe_list *) malloc (sizeof (struct pipe_list))) == NULL) |
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| 84 | return NULL; |
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| 85 | |||
| 86 | /* zero out elements to we'll get here */ |
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| 87 | l1->fd = 0; |
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| 88 | l1->fp = NULL; |
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| 89 | l1->next = NULL; |
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| 90 | |||
| 91 | /* if empty list - just grab new node */ |
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| 92 | if (!pl) |
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| 93 | pl = l1; |
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| 94 | else |
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| 95 | { |
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| 96 | /* otherwise, find last node in list */ |
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| 97 | ++(l1->fd); |
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| 98 | l2 = pl; |
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| 99 | while (l2->next) |
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| 100 | { |
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| 101 | ++(l1->fd); |
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| 102 | l2 = l2->next; |
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| 103 | }; |
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| 104 | /* add new node to list */ |
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| 105 | l2->next = l1; |
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| 106 | } |
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| 107 | |||
| 108 | /* stick in elements we know already */ |
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| 109 | strcpy (l1->mode, md); |
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| 110 | sprintf (l1->temp_name, "%s.%d", tn, l1->fd); |
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| 111 | |||
| 112 | /* if can save the program name, build temp file */ |
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| 113 | if ((l1->command = malloc(strlen(cm)+1))) |
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| 114 | { |
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| 115 | strcpy(l1->command, cm); |
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| 116 | /* if caller wants to read */ |
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| 117 | if (l1->mode[0] == 'r') |
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| 118 | { |
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| 119 | /* dup stdout */ |
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| 120 | if ((l1->fd = dup (fileno (stdout))) == EOF) |
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| 121 | l1->fp = NULL; |
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| 122 | else if (!(l1->fp = freopen (l1->temp_name, "wb", stdout))) |
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| 123 | l1->fp = NULL; |
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| 124 | else |
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| 125 | /* exec cmd */ |
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| 126 | if (system (cm) == EOF) |
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| 127 | l1->fp = NULL; |
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| 128 | /* reopen real stdout */ |
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| 129 | if (dup2 (l1->fd, fileno (stdout)) == EOF) |
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| 130 | { |
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| 131 | l1->fp = NULL; |
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| 132 | close(l1->fd); |
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| 133 | } |
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| 134 | else |
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| 135 | /* open file for reader */ |
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| 136 | l1->fp = fopen (l1->temp_name, l1->mode); |
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| 137 | } |
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| 138 | else |
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| 139 | /* if caller wants to write */ |
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| 140 | if (l1->mode[0] == 'w') |
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| 141 | /* open temp file */ |
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| 142 | l1->fp = fopen (l1->temp_name, l1->mode); |
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| 143 | else |
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| 144 | /* unknown mode */ |
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| 145 | l1->fp = NULL; |
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| 146 | } |
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| 147 | return l1->fp; /* return == NULL ? ERROR : OK */ |
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| 148 | } |
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| 149 | |||
| 150 | int |
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| 151 | pclose (FILE *pp) |
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| 152 | { |
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| 153 | struct pipe_list *l1, *l2; /* list pointers */ |
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| 154 | int retval=0; /* function return value */ |
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| 155 | |||
| 156 | /* if pointer is first node */ |
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| 157 | if (pl->fp == pp) |
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| 158 | { |
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| 159 | /* save node and take it out the list */ |
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| 160 | l1 = pl; |
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| 161 | pl = l1->next; |
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| 162 | } |
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| 163 | else |
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| 164 | /* if more than one node in list */ |
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| 165 | if (pl->next) |
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| 166 | { |
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| 167 | /* find right node */ |
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| 168 | for (l2 = pl, l1 = pl->next; l1; l2 = l1, l1 = l2->next) |
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| 169 | if (l1->fp == pp) |
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| 170 | break; |
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| 171 | |||
| 172 | /* take node out of list */ |
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| 173 | l2->next = l1->next; |
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| 174 | } |
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| 175 | else |
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| 176 | return -1; |
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| 177 | |||
| 178 | /* if FILE not in list - return error */ |
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| 179 | if (l1->fp == pp) |
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| 180 | { |
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| 181 | /* close the (hopefully) popen()ed file */ |
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| 182 | fclose (l1->fp); |
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| 183 | |||
| 184 | /* if pipe was opened to write */ |
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| 185 | if (l1->mode[0] == 'w') |
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| 186 | { |
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| 187 | /* dup stdin */ |
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| 188 | if ((l1->fd = dup (fileno (stdin))) == EOF) |
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| 189 | retval = -1; |
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| 190 | else |
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| 191 | /* open temp stdin */ |
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| 192 | if (!(l1->fp = freopen (l1->temp_name, "rb", stdin))) |
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| 193 | retval = -1; |
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| 194 | else |
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| 195 | /* exec cmd */ |
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| 196 | if (system (l1->command) == EOF) |
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| 197 | retval = -1; |
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| 198 | else |
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| 199 | { |
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| 200 | /* reopen stdin */ |
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| 201 | if (dup2 (l1->fd, fileno (stdin)) == EOF) |
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| 202 | retval = -1; |
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| 203 | close(l1->fd); |
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| 204 | } |
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| 205 | } |
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| 206 | else |
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| 207 | /* if pipe was opened to read */ |
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| 208 | if (l1->mode[0] == 'r') |
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| 209 | retval = 0; |
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| 210 | else |
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| 211 | /* invalid mode */ |
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| 212 | retval = -1; |
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| 213 | } |
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| 214 | remove (l1->temp_name); /* remove temporary file */ |
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| 215 | free (l1->command); /* dealloc memory */ |
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| 216 | free (l1); /* dealloc memory */ |
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| 217 | l1 = NULL; /* make pointer bogus */ |
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| 218 | |||
| 219 | return retval; /* retval==0 ? OK : ERROR */ |
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| 220 | } |