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Diffstat (limited to '')
| -rw-r--r-- | src/unistd/searchpath2.c | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/src/unistd/searchpath2.c b/src/unistd/searchpath2.c new file mode 100644 index 0000000..9921550 --- /dev/null +++ b/src/unistd/searchpath2.c @@ -0,0 +1,132 @@ +/** + * slibc — Yet another C library + * Copyright © 2015 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 +/* } */ + + + +/** + * 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 (2) 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 fall rules for + * the `exec`-functions are used: The current working + * directory, and the default value for $PATH. + * @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* searchpath2(const char* name, const char* fallback) +{ + 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 ((len = confstr(_CS_PATH, NULL, 0))) + { + path = malloc((2 + len) * sizeof(char)); + if (path == NULL) + goto fail; + if (!confstr(_CS_PATH, stpcpy(path, ".:"), len)) + free(path), path = NULL; + } + if (path == NULL) + path = strdup(".:/usr/local/bin:/bin:/usr/bin"); + } + 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), -1; + + fail: + saved_errno = errno; + free(path); + free(pathname); + errno = saved_errno; + return -1; +} + |