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      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 
    117