lib/fpopen.c

   1 /*
   2  * fpopen.c --- unlike the libc popen, it directly executes the
   3  * command instead of call out to the shell.
   4  *
   5  * Copyright Theodore Ts'o, 1996-1999.
   6  *
   7  * Permission to use this file is granted for any purposes, as long as
   8  * this copyright statement is kept intact and the author is not held
   9  * liable for any damages resulting from the use of this program.
  10  *
  11  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
  12  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  13  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
  14  * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
  15  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  16  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
  17  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
  18  * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  19  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  20  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
  21  * USE OF THIS SOFTWARE.
  22  */
  23
  24 #include "config.h"
  25 #include <unistd.h>
  26 #include <stdlib.h>
  27 #include <stdio.h>
  28 #include <errno.h>
  29 #include <string.h>
  30 #include <ctype.h>
  31
  32 #define MAX_ARGV 256
  33
  34 extern FILE *fpopen(const char *cmd, const char *mode);
  35
  36 FILE *fpopen(const char *cmd, const char *mode)
  37 {
  38         char    *argv[MAX_ARGV];
  39         int     i = 0;
  40         char    *buf, *prog = 0;
  41         char    *p;
  42         int     do_stdin, do_stderr = 0;
  43         int     fds[2];
  44         pid_t   pid;
  45
  46         if (!mode) {
  47                 errno = EFAULT;
  48                 return NULL;
  49         }
  50
  51         switch (*mode) {
  52         case 'r':
  53                 do_stdin = 0;
  54                 break;
  55         case 'w':
  56                 do_stdin = 1;
  57                 break;
  58         default:
  59                 errno = EINVAL;
  60                 return NULL;
  61         }
  62         switch (*(mode+1)) {
  63         case '&':
  64                 do_stderr = 1;
  65         }
  66
  67         /*
  68          * Create the argv vector....
  69          */
  70         buf = malloc(strlen(cmd)+1);
  71         if (!buf)
  72                 return NULL;
  73         strcpy(buf, cmd);
  74         p = buf;
  75         while (p && *p) {
  76                 if (isspace(*p)) {
  77                         p++;
  78                         continue;
  79                 }
  80                 if (i == 0)
  81                         prog = p;
  82                 argv[i++] = p;
  83                 p = strchr(p, ' ');
  84                 if (p)
  85                         *p++ = 0;
  86         }
  87
  88         argv[i] = 0;
  89
  90         /*
  91          * Get the pipe
  92          */
  93         if (pipe(fds) < 0)
  94                 return NULL;
  95
  96         /* Fork and execute the correct program. */
  97         if ((pid = fork()) < 0) {
  98                 perror("fork");
  99                 return NULL;
 100         } else if (pid == 0) {
 101                 if (do_stdin) {
 102                         close(fds[1]);
 103                         dup2(fds[0], 0);
 104                 } else {
 105                         close(fds[0]);
 106                         dup2(fds[1], 1);
 107                         if (do_stderr)
 108                                 dup2(fds[1], 2);
 109                 }
 110                 (void) execvp(prog, argv);
 111                 perror(prog);
 112                 exit(1);
 113         }
 114         return fdopen(do_stdin ? fds[1] : fds[0], mode);
 115 }
 116