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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 <unistd.h>
     25 #include <stdlib.h>
     26 #include <stdio.h>
     27 #include <errno.h>
     28 #include <string.h>
     29 #include <ctype.h>
     30 
     31 #define MAX_ARGV 256
     32 
     33 extern FILE *fpopen(const char *cmd, const char *mode);
     34 
     35 FILE *fpopen(const char *cmd, const char *mode)
     36 {
     37 	char	*argv[MAX_ARGV];
     38 	int	i = 0;
     39 	char	*buf, *prog = 0;
     40 	char	*p;
     41 	int	do_stdin, do_stderr = 0;
     42 	int	fds[2];
     43 	pid_t	pid;
     44 
     45 	if (!mode) {
     46 		errno = EFAULT;
     47 		return NULL;
     48 	}
     49 
     50 	switch (*mode) {
     51 	case 'r':
     52 		do_stdin = 0;
     53 		break;
     54 	case 'w':
     55 		do_stdin = 1;
     56 		break;
     57 	default:
     58 		errno = EINVAL;
     59 		return NULL;
     60 	}
     61 	switch (*(mode+1)) {
     62 	case '&':
     63 		do_stderr = 1;
     64 	}
     65 
     66 	/*
     67 	 * Create the argv vector....
     68 	 */
     69 	buf = malloc(strlen(cmd)+1);
     70 	if (!buf)
     71 		return NULL;
     72 	strcpy(buf, cmd);
     73 	p = buf;
     74 	while (p && *p) {
     75 		if (isspace(*p)) {
     76 			p++;
     77 			continue;
     78 		}
     79 		if (i == 0)
     80 			prog = p;
     81 		argv[i++] = p;
     82 		p = strchr(p, ' ');
     83 		if (p)
     84 			*p++ = 0;
     85 	}
     86 
     87 	argv[i] = 0;
     88 
     89 	/*
     90 	 * Get the pipe
     91 	 */
     92 	if (pipe(fds) < 0)
     93 		return NULL;
     94 
     95 	/* Fork and execute the correct program. */
     96 	if ((pid = fork()) < 0) {
     97 		perror("fork");
     98 		return NULL;
     99 	} else if (pid == 0) {
    100 		if (do_stdin) {
    101 			close(fds[1]);
    102 			dup2(fds[0], 0);
    103 		} else {
    104 			close(fds[0]);
    105 			dup2(fds[1], 1);
    106 			if (do_stderr)
    107 				dup2(fds[1], 2);
    108 		}
    109 		(void) execvp(prog, argv);
    110 		perror(prog);
    111 		exit(1);
    112 	}
    113 	return fdopen(do_stdin ? fds[1] : fds[0], mode);
    114 }
    115 
    116