libexplain  1.4.D001
libexplain/system_success_or_die.c
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00001 /*
00002  * libexplain - Explain errno values returned by libc functions
00003  * Copyright (C) 2008-2010, 2012, 2013 Peter Miller
00004  * Written by Peter Miller <pmiller@opensource.org.au>
00005  *
00006  * This program is free software; you can redistribute it and/or modify
00007  * it under the terms of the GNU Lesser General Public License as
00008  * published by the Free Software Foundation; either version 3 of the
00009  * License, or (at your option) any later version.
00010  *
00011  * This program is distributed in the hope that it will be useful,
00012  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00013  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00014  * Lesser General Public License for more details.
00015  *
00016  * You should have received a copy of the GNU Lesser General Public License
00017  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
00018  */
00019 
00020 #include <libexplain/ac/assert.h>
00021 #include <libexplain/ac/ctype.h>
00022 #include <libexplain/ac/errno.h>
00023 #include <libexplain/ac/limits.h> /* for PATH_MAX on Solaris */
00024 #include <libexplain/ac/stdlib.h>
00025 #include <libexplain/ac/string.h>
00026 #include <libexplain/ac/sys/param.h> /* for PATH_MAX except Solaris */
00027 #include <libexplain/ac/sys/wait.h>
00028 #include <libexplain/ac/unistd.h>
00029 
00030 #include <libexplain/buffer/errno/access.h>
00031 #include <libexplain/buffer/errno/fork.h>
00032 #include <libexplain/buffer/errno/system.h>
00033 #include <libexplain/buffer/errno/wait.h>
00034 #include <libexplain/buffer/wait_status.h>
00035 #include <libexplain/common_message_buffer.h>
00036 #include <libexplain/string_buffer.h>
00037 #include <libexplain/system.h>
00038 #include <libexplain/output.h>
00039 
00040 
00041 static int
00042 extract_command(const char *src, char *dst, size_t dst_size)
00043 {
00044     char *dst_end = dst + dst_size - 1;
00045     char *dp;
00046 
00047     for (;;)
00048     {
00049         if (!*src)
00050             break;
00051         if (isspace((unsigned char)*src))
00052         {
00053             ++src;
00054             continue;
00055         }
00056         dp = dst;
00057         for (;;)
00058         {
00059             if (dp < dst_end)
00060                 *dp++ = *src;
00061             ++src;
00062             if (!*src)
00063                 break;
00064             if (isspace((unsigned char)*src) || strchr("<>^|", *src))
00065             {
00066                 ++src;
00067                 break;
00068             }
00069         }
00070         *dp = '\0';
00071 
00072         /*
00073          * If there is an equals sign, it is probably an environment
00074          * variable setting before the command word.
00075          */
00076         if (strchr(dst, '='))
00077             continue;
00078 
00079         /*
00080          * Probably found the command, so long as it contains no shell
00081          * special characters.
00082          */
00083         return !strpbrk(dst, "!\"#$&'()*:;<>?[\\]^`{|}");
00084     }
00085     return 0;
00086 }
00087 
00088 
00089 static int
00090 command_on_path(const char *cmd)
00091 {
00092     char            combo[PATH_MAX * 2 + 3];
00093     explain_string_buffer_t combo_sb;
00094     const char      *path;
00095     const char      *start;
00096 
00097     path = getenv("PATH");
00098     if (!path)
00099         path = ".";
00100     for (;;)
00101     {
00102         start = path;
00103         for (;;)
00104         {
00105             if (*path == '\0')
00106                 break;
00107             if (*path == ':')
00108                 break;
00109             ++path;
00110         }
00111         explain_string_buffer_init(&combo_sb, combo, sizeof(combo));
00112         if (start == path)
00113             explain_string_buffer_putc(&combo_sb, '.');
00114         else
00115             explain_string_buffer_write(&combo_sb, start, path - start);
00116         explain_string_buffer_path_join(&combo_sb, cmd);
00117         if (access(combo, X_OK) >= 0)
00118             return 1;
00119         if (*path == '\0')
00120             return 0;
00121         assert(*path == ':');
00122         ++path;
00123     }
00124 }
00125 
00126 
00127 int
00128 explain_system_success(const char *command)
00129 {
00130     int             status;
00131 
00132     status = system(command);
00133     if (status < 0)
00134     {
00135         explain_output_error("%s", explain_system(command));
00136     }
00137     else if (status != 0)
00138     {
00139         explain_string_buffer_t sb;
00140         explain_string_buffer_init
00141         (
00142             &sb,
00143             explain_common_message_buffer,
00144             explain_common_message_buffer_size
00145         );
00146         explain_buffer_errno_system(&sb, 0, command);
00147 
00148         if (!command)
00149             command = "/bin/sh";
00150 
00151         /* FIXME: i18n */
00152         explain_string_buffer_puts(&sb, ", but ");
00153         explain_buffer_wait_status(&sb, status);
00154         if (WIFEXITED(status) && WEXITSTATUS(status) == 127)
00155         {
00156             char            cmd[PATH_MAX + 1];
00157 
00158             /*
00159              * It is possible that execl(2) used by system(3) failed,
00160              * and this could have caused the 127 exit status.  On the
00161              * other hand, the command itself could return this.
00162              */
00163             if (extract_command(command, cmd, sizeof(cmd)))
00164             {
00165                 if (strchr(cmd, '/'))
00166                 {
00167                     if (access(cmd, X_OK) < 0)
00168                     {
00169                         explain_string_buffer_puts(&sb, ", ");
00170                         explain_buffer_errno_access_explanation
00171                         (
00172                             &sb,
00173                             errno,
00174                             "system",
00175                             cmd,
00176                             X_OK
00177                         );
00178                     }
00179                 }
00180                 else if (!command_on_path(cmd))
00181                 {
00182                     explain_string_buffer_puts(&sb, ", ");
00183                     explain_string_buffer_puts_quoted(&sb, cmd);
00184                     explain_string_buffer_puts
00185                     (
00186                         &sb,
00187                         " command not found on $PATH"
00188                     );
00189                 }
00190             }
00191         }
00192         explain_output_error("%s", explain_common_message_buffer);
00193     }
00194     return status;
00195 }
00196 
00197 
00198 void
00199 explain_system_success_or_die(const char *command)
00200 {
00201     if (explain_system_success(command))
00202         explain_output_exit_failure();
00203 }
00204 
00205 
00206 /* vim: set ts=8 sw=4 et : */