Existence-Tests

.gitignore

/broken.lnk
/exists
.DS_Store

exists.c

#include <stdio.h>
#include <fcntl.h>
#include <sys/errno.h>
#include <sys/stat.h>
#include <unistd.h>

int main(int argc, const char *argv[]){
	const char *path;
	
	for(int i = 1; i < argc; ++i){
		path = argv[i];

#if defined(faccessat) && defined(AT_FDCWD) && defined(AT_SYMLINK_NOFOLLOW)
		if(faccessat(AT_FDCWD, path, F_OK, AT_SYMLINK_NOFOLLOW))
			goto nope;
#else
		int fd;
		if(-1 == open(path, O_RDONLY | O_SYMLINK, &fd))
			goto nope;
		close(fd);
#endif
		printf("%s exists\n", path);
	}
	return 0;
	
	nope:
		perror(argv[0]);
		return 1;
}

exists.mjs

#!/usr/bin/env node
/**
 * @fileoverview fs_usage(1) output
 */
import {existsSync, accessSync, constants, openSync, closeSync} from "fs";

closeSync(openSync("broken.lnk", constants.O_RDONLY | constants.O_SYMLINK));
// open   F=20   (R________S_X)  broken.lnk
// close  F=20

existsSync(process.argv[0]);                // access        (___F)    /usr/local/Cellar/node/16.7.0/bin/node
existsSync("/tmp/naaaah");                  // access  [  2] (___F)    private/tmp/naaaah
existsSync("/tmp/a.css");                   // access        (___F)    private/tmp/a.css
existsSync("broken.lnk");                   // access  [  2] (___F)    nowhere
accessSync("/tmp/a.css", constants.W_OK);   // access        (_W__)    private/tmp/a.css
accessSync("/tmp/a.css", constants.R_OK);   // access        (R___)    private/tmp/a.css
accessSync("/tmp/a.css", constants.F_OK);   // access        (___F)    private/tmp/a.css
accessSync("/tmp/a.css", constants.X_OK);   // access  [ 13] (__X_)    private/tmp/a.css

Makefile

all: broken.lnk exists

broken.lnk:
	ln -s nowhere $@

exists: exists.c
	cc -o $@ $^