/**
* slibc — Yet another C library
* Copyright © 2015, 2016 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
/* TODO temporary contants from other headers { */
#define _CS_PATH 1
/* } */
/**
* The default value for the PATH environment variable.
*/
#ifndef DEFAULT_PATH
# define DEFAULT_PATH "/usr/local/bin:/bin:/usr/bin"
#endif
/**
* Search the environment variable $PATH for an executable
* file whose name is the specified name. Slashes are ignored
* and treated as any other character. $PATH is searched
* for left to right, and ':' is used as the path-delimiter.
* If $PATH is not defined, a fallback value for $PATH will be
* used.
*
* $PATH is not inspected if `name` starts with './', '../', or '/'.
*
* This function was added because it was useful in implementing
* the `exec`-function family.
*
* This is a slibc extension.
*
* @etymology Variant of (searchpath) that takes (3) arguments.
*
* @param name The name of the sought executable. Must not be `NULL`.
* @param fallback Value to use instead of the value of $PATH, if
* path is not defined. If `NULL` the default value
* for $PATH is used.
* @param first If $PATH is not defined, and `fallback` is `NULL`,
* these directories are tested before the default
* directories. May be `NULL`.
* @return The pathname of the sought file, `NULL` on error,
* or if not found. Files that are not executable
* are (almost) ignored.
*
* @throws ENOMEM The process cannot allocate enough memory.
* @throws ENOENT There are no directories listed in $PATH, or
* the sought file is not exist inside $PATH.
* @throws EACCES None of the candidates (with at least one candidate)
* are executable by the current user.
* @throws Any exception defined for access(3), except for `EROFS`,
* these when encountered, the search is aborted, unless
* the error is `ENOENT` or `EACCES`.
*
* @since Always.
*/
char* searchpath3(const char* name, const char* fallback, const char* first)
{
char* path;
size_t len = 0;
char* pathname = NULL;
char* p;
char* q;
int eacces = 0;
int saved_errno;
if (strstarts(name, "./") || strstarts(name, "../") || strstarts(name, "/"))
{
if (access(name, X_OK) == 0)
return strdup(name);
return NULL;
}
path = getenv("PATH");
if ((path == NULL) && (fallback == NULL))
{
if (first == NULL)
first = "";
if ((len = confstr(_CS_PATH, NULL, 0)))
{
path = malloc((strlen(first) + 1 + len) * sizeof(char));
if (path == NULL)
goto fail;
if (!confstr(_CS_PATH, stpcpy(stpcpy(path, first), ":"), len))
free(path), path = NULL;
}
if (path == NULL)
{
path = malloc(strlen(first) * sizeof(char) + sizeof(":" DEFAULT_PATH));
if (path == NULL)
goto fail;
stpcpy(stpcpy(path, first), ":" DEFAULT_PATH);
}
}
else
path = strdup(path == NULL ? fallback : path);
if (path == NULL)
goto fail;
pathname = malloc((strlen(path) + strlen(name) + 2) * sizeof(char));
if (pathname == NULL)
goto fail;
for (p = path; *p; p = q + 1)
{
if (p == (q = strchr(p, ':')))
continue;
*q = '\0';
stpcpy(stpcpy(stpcpy(pathname, p), "/"), name);
if (access(pathname, X_OK) == 0)
{
char* truncated = realloc(pathname, (strlen(pathname) + 1) * sizeof(char));
return truncated == NULL ? pathname : truncated;
}
else if (errno == EACCES) eacces = 1;
else if (errno != ENOENT) goto fail;
}
free(path);
free(pathname);
return errno = (eacces ? EACCES : ENOENT), NULL;
fail:
saved_errno = errno;
free(path);
free(pathname);
errno = saved_errno;
return NULL;
}
