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90 lines
1.9 KiB
C
90 lines
1.9 KiB
C
/* C implementation of UNIX which(1)
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*
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* Copyright (c) 2017 Joachim Nilsson <troglobit@gmail.com>
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <errno.h>
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#include <stdio.h> /* snprintf() */
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#include <stdlib.h> /* realloc(), free() */
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#include <string.h> /* strtok_r() */
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#include <unistd.h> /* access() */
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/*
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* Like which(1), returns a malloc'ed path to cmd on success, or NULL
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*/
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char *which(const char *cmd)
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{
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size_t pathlen = 0;
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char *ptr, *tok, *env, *path = NULL;
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if (!cmd) {
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errno = EINVAL;
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return NULL;
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}
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if (cmd[0] == '/') {
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path = strdup(cmd);
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if (!access(path, X_OK))
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return path;
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if (path)
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free(path);
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return NULL;
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}
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ptr = getenv("PATH");
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if (!ptr)
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return NULL;
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env = strdup(ptr);
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if (!env)
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return NULL;
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tok = strtok_r(env, ":", &ptr);
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while (tok) {
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size_t len = strlen(tok) + strlen(cmd) + 2;
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if (pathlen < len) {
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path = realloc(path, len);
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if (!path) {
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free(env);
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return NULL;
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}
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pathlen = len;
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}
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snprintf(path, pathlen, "%s/%s", tok, cmd);
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if (!access(path, X_OK)) {
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free(env);
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return path;
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}
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tok = strtok_r(NULL, ":", &ptr);
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}
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if (path)
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free(path);
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free(env);
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return NULL;
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}
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/**
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* Local Variables:
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* indent-tabs-mode: t
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* c-file-style: "linux"
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* End:
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*/
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