minimum program

fileis/Makefile

@@ -0,0 +1,7 @@
+fileis: fileis.o libfileis.o
+	$(CC) $(CFLAGS) -o fileis fileis.o libfileis.o
+
+clean:
+	$(RM) fileis fileis.o libfileis.o
+
+.PHONY: clean

fileis/fileis.c

@@ -0,0 +1,34 @@
+#include <stdio.h> /* fprintf(3), stderr, NULL */
+#if !defined EX_OK || !defined EX_USAGE
+#	include <sysexits.h>
+#endif
+#include <unistd.h> /* getopt(3) */
+#include "libfileis.h" /* f_executable(3), f_exists(3), f_readable(3),
+                        * f_writeable(3) */
+
+static char *program_name = "fileis";
+
+int main(int argc, char *argv[]){
+	int c;
+	int (*f)(char *path);
+
+	if(argc < 2)
+		goto usage;
+
+	while((c = getopt(argc, argv, "erwx")) != -1)
+		switch(c){
+		case 'e': f = f_exists; break;
+		case 'r': f = f_readable; break;
+		case 'w': f = f_writeable; break;
+		case 'x': f = f_executable; break;
+		default:  goto usage;
+		}
+
+	if(optind == argc){
+usage:		fprintf(stderr, "Usage: %s (-ehrwx) [file]\n",
+			argv[0] == NULL ? program_name : argv[0]);
+		return EX_USAGE;
+	}
+
+	return !f(argv[optind]);
+}

fileis/libfileis.c

@@ -0,0 +1,7 @@
+#include "libfileis.h"
+#include <unistd.h> /* access(3), F_OK, R_OK, W_OK, X_OK */
+
+int f_executable(char *path){	return access(path, X_OK) == 0; }
+int f_exists(char *path){	return access(path, F_OK) == 0; }
+int f_readable(char *path){	return access(path, R_OK) == 0; }
+int f_writeable(char *path){	return access(path, W_OK) == 0; }

fileis/libfileis.h

@@ -0,0 +1,4 @@
+int f_executable(char *path);
+int f_exists(char *path);
+int f_readable(char *path);
+int f_writeable(char *path);