utils-std

realpath.c (4410B)

// utils-std: Collection of commonly available Unix tools
// SPDX-FileCopyrightText: 2017 Haelwenn (lanodan) Monnier <contact+utils@hacktivis.me>
// SPDX-License-Identifier: MPL-2.0
#define _POSIX_C_SOURCE 200809L
#define _XOPEN_SOURCE 700 // realpath is in XSI
#include "../lib/fs.h"
#include <errno.h>
#include <limits.h> // PATH_MAX
#include <stdbool.h>
#include <stdio.h>  // fprintf(), puts()
#include <stdlib.h> // realpath()
#include <string.h> // strncmp(), strnlen, strerror
#include <unistd.h> // getopt
static bool must_exists = false;
static char *argv0 = NULL;
static char sep = '\n';
static int
print_realpath(char *path)
{
	char *file = realpath(path, NULL);
	if(file)
	{
		if(printf("%s", file) < 0)
		{
			fprintf(stderr, "%s: Error writing to stdtout: %s\n", argv0, strerror(errno));
			free(file);
			return 1;
		}
		free(file);
		return 0;
	}
	if(must_exists || errno != ENOENT)
	{
		fprintf(stderr, "%s: Failed canonilizing \"%s\": %s\n", argv0, path, strerror(errno));
		return 1;
	}
	char *child = path_split_static(path, true);
	if(child == NULL)
	{
		// Return as if realpath just failed
		fprintf(stderr, "%s: Failed canonilizing \"%s\": %s\n", argv0, path, strerror(errno));
		return 1;
	}
	errno = 0;
	char *parent = realpath(path, NULL);
	if(!parent)
	{
		fprintf(stderr,
		        "%s: Failed canonilizing parent of full path \"%s/%s\": %s\n",
		        argv0,
		        path,
		        child,
		        strerror(errno));
		return 1;
	}
	if(printf("%s/%s", parent, child) < 0)
	{
		fprintf(stderr, "%s: Error writing to stdtout: %s\n", argv0, strerror(errno));
		free(parent);
		return 1;
	}
	free(parent);
	return 0;
}
static void
usage_realpath(void)
{
	fprintf(stderr, "Usage: realpath [-E|-e] [-n|-z] path...\n");
}
static int
main_realpath(int argc, char *argv[])
{
	must_exists = false;
	int offset_sep = 0;
	int c = -1;
	while((c = getopt(argc, argv, ":Eemnz")) != -1)
	{
		switch(c)
		{
		case 'E':
			must_exists = false;
			break;
		case 'e':
			must_exists = true;
			break;
		case 'n':
			offset_sep = 1;
			break;
		case 'z':
			sep = '\0';
			break;
		case ':':
			fprintf(stderr, "realpath: Error: Missing operand for option: '-%c'\n", optopt);
			usage_realpath();
			return 1;
		case '?':
			fprintf(stderr, "realpath: Error: Unrecognised option: '-%c'\n", optopt);
			usage_realpath();
			return 1;
		}
	}
	argv += optind;
	argc -= optind;
	if(argc == 0)
	{
		fprintf(stderr, "%s: Expected one file as argument, got 0\n", argv0);
		usage_realpath();
		return 1;
	}
	for(int i = 0; i < argc; i++)
	{
		if(print_realpath(argv[i]) != 0) return 1;
		if(i != argc - offset_sep) printf("%c", sep);
	}
	return 0;
}
static void
usage_readlink(void)
{
	fprintf(stderr, "Usage: readlink [-f|-e] [-n|-z] file...\n");
}
static int
main_readlink(int argc, char *argv[])
{
	must_exists = true;
	bool canonicalize = false;
	int offset_sep = 0;
	int c = -1;
	while((c = getopt(argc, argv, ":femnz")) != -1)
	{
		switch(c)
		{
		case 'f':
			canonicalize = true;
			must_exists = false;
			break;
		case 'e':
			must_exists = true;
			break;
		case 'n':
			offset_sep = 1;
			break;
		case 'z':
			sep = '\0';
			break;
		case ':':
			fprintf(stderr, "readlink: Error: Missing operand for option: '-%c'\n", optopt);
			usage_readlink();
			return 1;
		case '?':
			fprintf(stderr, "readlink: Error: Unrecognised option: '-%c'\n", optopt);
			usage_readlink();
			return 1;
		}
	}
	argv += optind;
	argc -= optind;
	if(argc == 0)
	{
		fprintf(stderr, "%s: Expected one file as argument, got 0\n", argv0);
		usage_readlink();
		return 1;
	}
	for(int i = 0; i < argc; i++)
	{
		char *path = argv[i];
		if(canonicalize)
		{
			if(print_realpath(path) != 0) return 1;
			if(i != argc) printf("%c", sep);
			continue;
		}
		char buf[PATH_MAX] = "";
		if(readlink(path, buf, sizeof(buf) - 1) < 0)
		{
			fprintf(stderr,
			        "readlink: Error: Failed reading symbolic link of '%s': %s\n",
			        path,
			        strerror(errno));
			return 1;
		}
		printf("%s", buf);
		if(i != argc - offset_sep) printf("%c", sep);
	}
	return 0;
}
int
main(int argc, char *argv[])
{
	argv0 = static_basename(argv[0]);
	if(strcmp(argv0, "realpath") == 0) return main_realpath(argc, argv);
	if(strcmp(argv0, "readlink") == 0) return main_readlink(argc, argv);
	fprintf(stderr, "Unknown utility '%s', expected realpath or readlink\n", argv0);
	return 1;
}