lib/findprog.c

   1 /* Locating a program in PATH.
   2    Copyright (C) 2001-2004, 2006-2020 Free Software Foundation, Inc.
   3    Written by Bruno Haible <haible@clisp.cons.org>, 2001.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18
  19 #include <config.h>
  20
  21 /* Specification.  */
  22 #include "findprog.h"
  23
  24 #include <stdbool.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28
  29 /* Avoid collision between findprog.c and findprog-lgpl.c.  */
  30 #if IN_FINDPROG_LGPL || ! GNULIB_FINDPROG_LGPL
  31
  32 #if !IN_FINDPROG_LGPL
  33 # include "xalloc.h"
  34 #endif
  35 #include "concat-filename.h"
  36
  37
  38 const char *
  39 find_in_path (const char *progname)
  40 {
  41 #if defined _WIN32 || defined __CYGWIN__ || defined __EMX__ || defined __DJGPP__
  42   /* Native Windows, Cygwin, OS/2, DOS */
  43   /* The searching rules with .COM, .EXE, .BAT, .CMD etc. suffixes are
  44      too complicated.  Leave it to the OS.  */
  45   return progname;
  46 #else
  47   /* Unix */
  48   char *path;
  49   char *path_rest;
  50   char *cp;
  51
  52   if (strchr (progname, '/') != NULL)
  53     /* If progname contains a slash, it is either absolute or relative to
  54        the current directory.  PATH is not used.  */
  55     return progname;
  56
  57   path = getenv ("PATH");
  58   if (path == NULL || *path == '\0')
  59     /* If PATH is not set, the default search path is implementation
  60        dependent.  */
  61     return progname;
  62
  63   /* Make a copy, to prepare for destructive modifications.  */
  64 # if !IN_FINDPROG_LGPL
  65   path = xstrdup (path);
  66 # else
  67   path = strdup (path);
  68   if (path == NULL)
  69     /* Out of memory.  */
  70     return progname;
  71 # endif
  72   for (path_rest = path; ; path_rest = cp + 1)
  73     {
  74       const char *dir;
  75       bool last;
  76       char *progpathname;
  77
  78       /* Extract next directory in PATH.  */
  79       dir = path_rest;
  80       for (cp = path_rest; *cp != '\0' && *cp != ':'; cp++)
  81         ;
  82       last = (*cp == '\0');
  83       *cp = '\0';
  84
  85       /* Empty PATH components designate the current directory.  */
  86       if (dir == cp)
  87         dir = ".";
  88
  89       /* Concatenate dir and progname.  */
  90 # if !IN_FINDPROG_LGPL
  91       progpathname = xconcatenated_filename (dir, progname, NULL);
  92 # else
  93       progpathname = concatenated_filename (dir, progname, NULL);
  94       if (progpathname == NULL)
  95         {
  96           /* Out of memory.  */
  97           free (path);
  98           return progname;
  99         }
 100 # endif
 101
 102       /* On systems which have the eaccess() system call, let's use it.
 103          On other systems, let's hope that this program is not installed
 104          setuid or setgid, so that it is ok to call access() despite its
 105          design flaw.  */
 106       if (eaccess (progpathname, X_OK) == 0)
 107         {
 108           /* Found!  */
 109           if (strcmp (progpathname, progname) == 0)
 110             {
 111               free (progpathname);
 112
 113               /* Add the "./" prefix for real, that xconcatenated_filename()
 114                  optimized away.  This avoids a second PATH search when the
 115                  caller uses execlp/execvp.  */
 116               progpathname = XNMALLOC (2 + strlen (progname) + 1, char);
 117               progpathname[0] = '.';
 118               progpathname[1] = '/';
 119               memcpy (progpathname + 2, progname, strlen (progname) + 1);
 120             }
 121
 122           free (path);
 123           return progpathname;
 124         }
 125
 126       free (progpathname);
 127
 128       if (last)
 129         break;
 130     }
 131
 132   /* Not found in PATH.  An error will be signalled at the first call.  */
 133   free (path);
 134   return progname;
 135 #endif
 136 }
 137
 138 #endif