libiberty/pex-unix.c

   1 /* Utilities to execute a program in a subprocess (possibly linked by pipes
   2    with other subprocesses), and wait for it.  Generic Unix version
   3    (also used for UWIN and VMS).
   4    Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2003
   5    Free Software Foundation, Inc.
   6
   7 This file is part of the libiberty library.
   8 Libiberty is free software; you can redistribute it and/or
   9 modify it under the terms of the GNU Library General Public
  10 License as published by the Free Software Foundation; either
  11 version 2 of the License, or (at your option) any later version.
  12
  13 Libiberty is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16 Library General Public License for more details.
  17
  18 You should have received a copy of the GNU Library General Public
  19 License along with libiberty; see the file COPYING.LIB.  If not,
  20 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  21 Boston, MA 02111-1307, USA.  */
  22
  23 #include "pex-common.h"
  24
  25 #include <stdio.h>
  26 #include <errno.h>
  27 #ifdef NEED_DECLARATION_ERRNO
  28 extern int errno;
  29 #endif
  30 #ifdef HAVE_STRING_H
  31 #include <string.h>
  32 #endif
  33 #ifdef HAVE_UNISTD_H
  34 #include <unistd.h>
  35 #endif
  36 #ifdef HAVE_STDLIB_H
  37 #include <stdlib.h>
  38 #endif
  39 #ifdef HAVE_SYS_WAIT_H
  40 #include <sys/wait.h>
  41 #endif
  42
  43 #ifndef HAVE_WAITPID
  44 #define waitpid(pid, status, flags) wait(status)
  45 #endif
  46
  47 extern int execv ();
  48 extern int execvp ();
  49
  50 int
  51 pexecute (program, argv, this_pname, temp_base, errmsg_fmt, errmsg_arg, flags)
  52      const char *program;
  53      char * const *argv;
  54      const char *this_pname;
  55      const char *temp_base ATTRIBUTE_UNUSED;
  56      char **errmsg_fmt, **errmsg_arg;
  57      int flags;
  58 {
  59   int (*func)() = (flags & PEXECUTE_SEARCH ? execvp : execv);
  60   int pid;
  61   int pdes[2];
  62   int input_desc, output_desc;
  63   int retries, sleep_interval;
  64   /* Pipe waiting from last process, to be used as input for the next one.
  65      Value is STDIN_FILE_NO if no pipe is waiting
  66      (i.e. the next command is the first of a group).  */
  67   static int last_pipe_input;
  68
  69   /* If this is the first process, initialize.  */
  70   if (flags & PEXECUTE_FIRST)
  71     last_pipe_input = STDIN_FILE_NO;
  72
  73   input_desc = last_pipe_input;
  74
  75   /* If this isn't the last process, make a pipe for its output,
  76      and record it as waiting to be the input to the next process.  */
  77   if (! (flags & PEXECUTE_LAST))
  78     {
  79       if (pipe (pdes) < 0)
  80         {
  81           *errmsg_fmt = "pipe";
  82           *errmsg_arg = NULL;
  83           return -1;
  84         }
  85       output_desc = pdes[WRITE_PORT];
  86       last_pipe_input = pdes[READ_PORT];
  87     }
  88   else
  89     {
  90       /* Last process.  */
  91       output_desc = STDOUT_FILE_NO;
  92       last_pipe_input = STDIN_FILE_NO;
  93     }
  94
  95   /* Fork a subprocess; wait and retry if it fails.  */
  96   sleep_interval = 1;
  97   pid = -1;
  98   for (retries = 0; retries < 4; retries++)
  99     {
 100       pid = fork ();
 101       if (pid >= 0)
 102         break;
 103       sleep (sleep_interval);
 104       sleep_interval *= 2;
 105     }
 106
 107   switch (pid)
 108     {
 109     case -1:
 110       *errmsg_fmt = "fork";
 111       *errmsg_arg = NULL;
 112       return -1;
 113
 114     case 0: /* child */
 115       /* Move the input and output pipes into place, if necessary.  */
 116       if (input_desc != STDIN_FILE_NO)
 117         {
 118           close (STDIN_FILE_NO);
 119           dup (input_desc);
 120           close (input_desc);
 121         }
 122       if (output_desc != STDOUT_FILE_NO)
 123         {
 124           close (STDOUT_FILE_NO);
 125           dup (output_desc);
 126           close (output_desc);
 127         }
 128
 129       /* Close the parent's descs that aren't wanted here.  */
 130       if (last_pipe_input != STDIN_FILE_NO)
 131         close (last_pipe_input);
 132
 133       /* Exec the program.  */
 134       (*func) (program, argv);
 135
 136       fprintf (stderr, "%s: ", this_pname);
 137       fprintf (stderr, install_error_msg, program);
 138       fprintf (stderr, ": %s\n", xstrerror (errno));
 139       exit (-1);
 140       /* NOTREACHED */
 141       return 0;
 142
 143     default:
 144       /* In the parent, after forking.
 145          Close the descriptors that we made for this child.  */
 146       if (input_desc != STDIN_FILE_NO)
 147         close (input_desc);
 148       if (output_desc != STDOUT_FILE_NO)
 149         close (output_desc);
 150
 151       /* Return child's process number.  */
 152       return pid;
 153     }
 154 }
 155
 156 int
 157 pwait (pid, status, flags)
 158      int pid;
 159      int *status;
 160      int flags ATTRIBUTE_UNUSED;
 161 {
 162   /* ??? Here's an opportunity to canonicalize the values in STATUS.
 163      Needed?  */
 164   pid = waitpid (pid, status, 0);
 165   return pid;
 166 }