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// Copyright 2015 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// realpath.c
//
// A simple implementation of realpath for Mac OS X.
// This implementation follows gnu/linux conventions and allows the last
// component to not exist:
// http://www.gnu.org/software/coreutils/manual/html_node/realpath-invocation.html
// Debian requires all components to exist.
//
#include <errno.h>
#include <libgen.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
// Print a simple error message and exit.
static void PrintError(const char *argv[]) {
fprintf(stderr, "%s: %s\n", argv[1], strerror(errno));
exit(1);
}
// Concatenate two paths together adding a '/' if appropriate.
// Returned pointer is owned by client and should be freed.
static char *JoinPaths(const char *path1, const char* path2) {
size_t len1 = strlen(path1);
size_t len2 = strlen(path2);
// +1 for '/' and +1 for '\0'
size_t totalSize = len1 + 1 + len2 + 1;
char *outPath = malloc(totalSize);
if (outPath == NULL) {
return NULL;
}
strlcpy(outPath, path1, totalSize);
if (len1 > 0 && len2 > 0) {
if (path1[len1 - 1] != '/' && path2[0] != '/') {
strlcat(outPath, "/", totalSize);
}
}
strlcat(outPath, path2, totalSize);
return outPath;
}
// Since this is a simple utility that quits immediately, we are not worrying
// about making the code more complex by freeing up any memory allocations.
int main(int argc, const char *argv[]) {
if (argc != 2) {
fprintf(stderr, "realpath <path>\n");
return 1;
}
const char *path = argv[1];
char *goodPath = realpath(path, NULL);
if (goodPath == NULL) {
if ((errno != ENOENT) || (strlen(path) == 0)) {
PrintError(argv);
}
// If only the last element is missing, then call realpath on the parent
// dir and append the basename back onto it.
// Technically the strdup is not required on Mac OS X, but this
// keeps things compatible with other basename/dirname implementations
// that do require a string they can modify.
char *dirCopy = strdup(path);
char *baseCopy = strdup(path);
if (dirCopy == NULL || baseCopy == NULL) {
PrintError(argv);
}
char *dir = dirname(dirCopy);
if (dir == NULL) {
PrintError(argv);
}
char *base = basename(baseCopy);
if (base == NULL) {
PrintError(argv);
}
char *realdir = realpath(dir, NULL);
if (realdir == NULL) {
PrintError(argv);
}
goodPath = JoinPaths(realdir, base);
if (goodPath == NULL) {
PrintError(argv);
}
}
fprintf(stdout, "%s\n", goodPath);
return 0;
}
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