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/* ----------------------------------------------------------------------------
* search path search logic
* (c) Ben Gamari 2021
*/
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>
#include "common.h"
// the below is only necessary when we need to emulate execvpe.
#if !defined(HAVE_EXECVPE)
/* A quick check for whether the given path is absolute. */
static bool is_absolute(const char *path) {
return path[0] == '/';
}
static char *concat_paths(const char *path1, const char *path2) {
if (is_absolute(path2)) {
return strdup(path2);
} else {
int len = strlen(path1) + 1 + strlen(path2) + 1;
char *tmp = malloc(len);
int ret = snprintf(tmp, len, "%s/%s", path1, path2);
if (ret < 0) {
free(tmp);
return NULL;
}
return tmp;
}
}
/* Return true if the given file exists and is an executable, optionally
* relative to the given working directory.
*/
static bool is_executable(char *working_dir, const char *path) {
if (working_dir && !is_absolute(path)) {
char *tmp = concat_paths(working_dir, path);
bool ret = access(tmp, X_OK) == 0;
free(tmp);
return ret;
} else {
return access(path, X_OK) == 0;
}
}
/* Find an executable with the given filename in the given search path. The
* result must be freed by the caller. Returns NULL if a matching file is not
* found.
*/
static char *find_in_search_path(char *working_dir, char *search_path, const char *filename) {
const int filename_len = strlen(filename);
char *tokbuf;
char *path = strtok_r(search_path, ":", &tokbuf);
if (!working_dir)
working_dir = ".";
int workdir_len = strlen(working_dir);
while (path != NULL) {
// N.B. gcc 6.3.0, used by Debian 9, inexplicably warns that `path`
// may not be initialised with -Wall. Silence this warning. See #210.
#if defined(__GNUC__) && __GNUC__ == 6 && __GNUC_MINOR__ == 3
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
#endif
char *tmp;
if (is_absolute(path)) {
const int tmp_len = strlen(path) + 1 + filename_len + 1;
tmp = malloc(tmp_len);
snprintf(tmp, tmp_len, "%s/%s", path, filename);
} else {
const int tmp_len = workdir_len + 1 + strlen(path) + 1 + filename_len + 1;
tmp = malloc(tmp_len);
snprintf(tmp, tmp_len, "%s/%s/%s", working_dir, path, filename);
}
#if defined(__GNUC__) && __GNUC__ == 6 && __GNUC_MINOR__ == 3
#pragma GCC diagnostic pop
#endif
if (is_executable(working_dir, tmp)) {
return tmp;
} else {
free(tmp);
}
path = strtok_r(NULL, ":", &tokbuf);
}
return NULL;
}
/* Identify the executable search path. The result must be freed by the caller. */
static char *get_executable_search_path(void) {
char *search_path;
search_path = getenv("PATH");
if (search_path) {
search_path = strdup(search_path);
return search_path;
}
#if defined(HAVE_CONFSTR)
int len = confstr(_CS_PATH, NULL, 0);
search_path = malloc(len + 1)
if (search_path != NULL) {
search_path[0] = ':';
(void) confstr (_CS_PATH, search_path + 1, len);
return search_path;
}
#endif
return strdup(":");
}
/* Find the given executable in the executable search path relative to
* workingDirectory (or the current directory, if NULL).
* N.B. the caller is responsible for free()ing the result.
*/
char *find_executable(char *working_dir, char *filename) {
/* Drop trailing slash from working directory if necessary */
if (working_dir) {
int workdir_len = strlen(working_dir);
if (working_dir[workdir_len-1] == '/') {
working_dir[workdir_len-1] = '\0';
}
}
if (is_absolute(filename)) {
/* If it's an absolute path name, it's easy. */
return filename;
} else if (strchr(filename, '/')) {
/* If it's a relative path name, we must look for executables relative
* to the working directory. */
if (is_executable(working_dir, filename)) {
return filename;
}
}
/* Otherwise look through the search path... */
char *search_path = get_executable_search_path();
char *result = find_in_search_path(working_dir, search_path, filename);
free(search_path);
return result;
}
#endif
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