automount/util.c

/*
 * MIT License
 * 
 * Copyright (c) 2020 Alessandro Mauri
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <limits.h>
#include "util.h"

/* Exit printing an error message and error string based on errno */
void die(const char *fmt, ...)
{
	va_list ap;
	va_start(ap, fmt);

	fputs(ANSI_COLOR_RED, stderr);
     	vfprintf(stderr, fmt, ap);

	if (fmt[0] && fmt[strlen(fmt) - 1] == ':') {
		fputc(' ', stderr);
		perror(NULL);
	} else {
		fputc('\n', stderr);
	}
     	fputs(ANSI_COLOR_RESET, stderr);

	va_end(ap);
	exit(errno ? errno : 1);
}

/* Prints the command usage flags and brief description */
void usage (void)
{
	puts("Usage:  automount [-h]\n"
	      "-h      print this message\n");
}

/* If the supplied path is a link, it returns the real absolute path, else it
 * returns the supplied path
 */
const char * get_path (const char *sym)
{
	static char buf[PATH_MAX];
	memset(buf, 0, 256);

	if (!realpath(sym, buf) || *buf == '0')
		return sym;
	if (buf[255])
		return NULL;

	return buf;
}

/* Check if file exists using stat, returns 0 if file does not exist or st_mode
 * if the file (or folder) exists, this way one could evaluate the type of file
 * without a second stat call, on error -1 is returned and errno is set
 */
int file_exists (const char *path)
{
	static struct stat st;
	if (stat(path, &st) < 0) {
		if (errno == ENOENT)
			return 0;
		else
			return -1;
	}
	return (int)st.st_mode;
}