Create which command

programs/Makefile

@@ -1,5 +1,7 @@
 .PHONY: default clean force_look
 
+PROGRAMS=one hello long loop longone longtwo keyboard tsh cpuid shutdown reboot args stat cat which
+
 default: dist
 
 tlib/libtlib.a: force_look
@@ -47,7 +49,10 @@ stat: force_look tlib/libtlib.a
 cat: force_look tlib/libtlib.a
 	cd cat; $(MAKE) cat
 
-dist: one hello long loop longone longtwo keyboard tsh cpuid shutdown reboot args stat cat
+which: force_look tlib/libtlib.a
+	cd which; $(MAKE) which
+
+dist: $(PROGRAMS)
 	mkdir -p dist
 	cp one/a.out dist/one
 	cp hello/a.out dist/hello
@@ -63,6 +68,7 @@ dist: one hello long loop longone longtwo keyboard tsh cpuid shutdown reboot arg
 	cp args/args dist/
 	cp stat/stat dist/
 	cp cat/cat dist/
+	cp which/which dist/
 	strip dist/*
 
 force_look:
@@ -83,4 +89,5 @@ clean:
 	cd args; $(MAKE) clean
 	cd stat; $(MAKE) clean
 	cd cat; $(MAKE) clean
+	cd which; $(MAKE) clean
 	rm -rf dist

programs/which/Makefile

@@ -0,0 +1,15 @@
+.PHONY: default clean
+
+default: which
+
+include ../../cpp.mk
+
+%.cpp.o: src/%.cpp
+	$(CC) -c $< -o $@ $(PROGRAM_FLAGS)
+
+which: main.cpp.o
+	$(CC) -o which main.cpp.o $(PROGRAM_LINK_FLAGS)
+
+clean:
+	rm -f *.cpp.o
+	rm -rf which

programs/which/src/main.cpp

@@ -0,0 +1,40 @@
+//=======================================================================
+// Copyright Baptiste Wicht 2013-2014.
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt)
+//=======================================================================
+
+#include <file.hpp>
+#include <system.hpp>
+#include <errors.hpp>
+#include <print.hpp>
+
+int main(int argc, char* argv[]){
+    if(argc == 1){
+        print_line("Usage: which executable_path");
+        exit(1);
+    }
+
+    std::string path(argv[1]);
+
+    if(path[0] != '/'){
+        path = "/bin/" + path;
+    }
+
+    auto fd = open(path.c_str());
+
+    if(fd.valid()){
+        print(path);
+
+        close(*fd);
+    } else {
+        if(fd.has_error(std::ERROR_NOT_EXISTS)){
+            printf("%s not found\n", argv[1]);
+        } else {
+            printf("which: error: %s\n", std::error_message(fd.error()));
+        }
+    }
+
+    exit(0);
+}