utils-std

mktemp.c (4768B)

// utils-std: Collection of commonly available Unix tools
// SPDX-FileCopyrightText: 2017 Haelwenn (lanodan) Monnier <contact+utils@hacktivis.me>
// SPDX-License-Identifier: MPL-2.0
// getentropy got in POSIX.1-2024 but defining _POSIX_C_SOURCE causes too much side-effects
#define _DEFAULT_SOURCE // getentropy
#include "../config.h"  // HAS_*
#include "../libutils/getopt_nolong.h"
#include "../libutils/lib_string.h"
#include <errno.h>
#include <limits.h> // PATH_MAX
#include <stdbool.h>
#include <stdio.h>  // fprintf
#include <stdlib.h> // getenv
#include <string.h> // strerror
#include <unistd.h> // getopt, getentropy
#ifdef HAS_GETOPT_LONG
#include <getopt.h>
#endif
const char *argv0 = "mktemp";
static int
unsafe_mktemp(char *template, size_t suffix)
{
	size_t l = strlen(template);
	size_t len = 0;
	size_t off = l - 1 - suffix;
	while(off > 0 && template[off] == 'X')
		off--, len++;
	if(len < 6)
	{
		fprintf(stderr,
		        "%s: error: Template '%s' is invalid (need >= 6 final X, got %zd)\n",
		        argv0,
		        template,
		        len);
		return 1;
	}
	for(size_t i = 0; i < l; i++)
	{
		if(template[i] == '\n')
		{
			fprintf(stderr, "%s: error: Invalid character (newline) in template\n", argv0);
			return 1;
		}
	}
	for(int retries = 100; 0 < retries; retries--)
	{
		unsigned long r = 0;
		if(getentropy(&r, sizeof(r)) != 0)
		{
			fprintf(stderr,
			        "%s: error: Failed to get entropy for random filename: %s\n",
			        argv0,
			        strerror(errno));
			return 1;
		}
		for(int i = len; i > 0; i--, r >>= 5)
			template[off + i] = 'A' + (r & 15) + (r & 16) * 2;
		if(access(template, F_OK) != 0 && errno == ENOENT)
		{
			puts(template);
			return 0;
		}
	}
	fprintf(stderr, "%s: error: Exhausted all 100 attempts at generating a filename\n", argv0);
	return 1;
}
int
main(int argc, char *argv[])
{
	bool o_create_dir = false, o_quiet = false, o_unsafe = false;
	static char template[PATH_MAX] = "./tmp.XXXXXXXXXX";
	const char *tmpdir = NULL;
#ifdef HAS_GETOPT_LONG
	// Strictly for GNUisms compatibility so no long-only options
	// clang-format off
	static struct option opts[] = {
		{"directory", no_argument, NULL, 'd'},
		{"dry-run", required_argument, NULL, 'u'},
		{"quiet", no_argument, NULL, 'q'},
		{"tmpdir", required_argument, NULL, 'p'},
		{0, 0, 0, 0},
	};
	// clang-format on
	// Need + as first character to get POSIX-style option parsing
	for(int c = -1; (c = getopt_long(argc, argv, "+:dqp:tu", opts, NULL)) != -1;)
#else
	for(int c = -1; (c = getopt_nolong(argc, argv, ":dqp:tu")) != -1;)
#endif
	{
		switch(c)
		{
		case 'd':
			o_create_dir = true;
			break;
		case 'q':
			o_quiet = true;
			break;
		case 'p':
			tmpdir = optarg;
			break;
		case 't':
			if(tmpdir == NULL) tmpdir = getenv("TMPDIR");
			if(tmpdir == NULL) tmpdir = "/tmp";
			break;
		case 'u':
			o_unsafe = true;
			break;
		case '?':
			GETOPT_UNKNOWN_OPT
			return 1;
		default:
			fprintf(stderr, "%s: error: Unhandled getopt case '%c'\n", argv0, c);
			abort();
		}
	}
	argc -= optind;
	argv += optind;
	if(argc == 1)
	{
		lib_strlcpy(template, *argv, PATH_MAX);
	}
	else if(argc > 1)
	{
		fprintf(stderr, "%s: error: Only one template argument is supported, got %d\n", argv0, argc);
		return 1;
	}
	if(tmpdir)
	{
		if(chdir(tmpdir) < 0)
		{
			fprintf(stderr,
			        "%s: error: Failed changing directory into tmpdir '%s': %s\n",
			        argv0,
			        tmpdir,
			        strerror(errno));
			return 1;
		}
		printf("%s/", tmpdir);
	}
	char *suffix_start = strrchr(template, 'X');
	if(!suffix_start)
	{
		fprintf(stderr, "%s: error: template '%s' does not contains any 'X'\n", argv0, template);
		return 1;
	}
	size_t suffix_len = strlen(suffix_start + 1);
	static char template_copy[PATH_MAX] = "";
	memcpy(template_copy, template, PATH_MAX);
	if(o_unsafe) return unsafe_mktemp(template, suffix_len);
	if(o_create_dir)
	{
#ifdef HAS_MKDTEMPS
		char *dir = mkdtemps(template, suffix_len);
#else
		char *dir = mkdtemp(template);
#endif
		if(dir == NULL)
		{
			if(!o_quiet)
				fprintf(stderr,
				        "%s: error: Failed creating random directory with template '%s': %s\n",
				        argv0,
				        template_copy,
				        strerror(errno));
			return 1;
		}
		puts(dir);
		return 0;
	}
#ifdef HAS_MKSTEMPS
	int fd = mkstemps(template, suffix_len);
#else
	int fd = mkstemp(template);
#endif
	if(fd < 0)
	{
		if(!o_quiet)
			fprintf(stderr,
			        "%s: error: Failed creating random file with template '%s': %s\n",
			        argv0,
			        template_copy,
			        strerror(errno));
		return 1;
	}
	puts(template);
	if(close(fd) < 0)
	{
		if(!o_quiet) fprintf(stderr, "%s: error: Failed closing file: %s\n", argv0, strerror(errno));
		return 1;
	}
	return 0;
}