CMake does not find custom command “ls”

Question

I try to run some basic commands for my CLion projects, but it just doesn't work. Here is my CMake setting.

cmake_minimum_required(VERSION 3.6)
project(hello)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")

set(SOURCE_FILES main.cpp)
add_executable(hello ${SOURCE_FILES})

add_custom_command(OUTPUT hello.out
        COMMAND ls -l hello
        DEPENDS hello)

add_custom_target(run_hello_out
        DEPENDS hello.out)

I got the following error messages when running run_hello_out in CLion.

[100%] Generating hello.out
process_begin: CreateProcess(NULL, ls -l hello, ...) failed.
make (e=2): The system cannot find the file specified.
mingw32-make.exe[3]: *** [hello.out] Error 2
mingw32-make.exe[2]: *** [CMakeFiles/run_hello_out.dir/all] Error 2
mingw32-make.exe[1]: *** [CMakeFiles/run_hello_out.dir/rule] Error 2
mingw32-make.exe: *** [run_hello_out] Error 2
CMakeFiles\run_hello_out.dir\build.make:59: recipe for target 'hello.out' failed
CMakeFiles\Makefile2:66: recipe for target 'CMakeFiles/run_hello_out.dir/all' failed
CMakeFiles\Makefile2:73: recipe for target 'CMakeFiles/run_hello_out.dir/rule' failed
Makefile:117: recipe for target 'run_hello_out' failed

It is supposed to run "ls -l hello" and see the results in either build window or run window.

Answer 1

Somehow ls doesn't work even I set up the global path correctly. CMake needs full path. The following works and solves the issue.

add_custom_command(OUTPUT hello.out
        COMMAND "C:\\FULL PATH HERE\\ls" -l hello
        DEPENDS hello)

Answer 2

The Problem

CMake doesn't guaranty a shell context for its COMMAND calls and it doesn't automatically search for the executable given with COMMAND itself.

It mainly puts the given command into the generated build environment and depends on how it's handled there.

In your case I assume you/CLion is running cmake and mingw32-make in a MS Windows cmd shell. In this case you would have had to use the dir instead of the ls command:

add_custom_target(
    run_hello_out
    COMMAND dir $<TARGET_FILE_NAME:hello>
    DEPENDS hello
)

Possible Soltions

I see three possible solutions. Either

1. Provide a bash shell context

   include(FindUnixCommands)
   
   if (BASH)
       add_custom_target(
           run_hello_out
           COMMAND ${BASH} -c "ls -l hello"
           DEPENDS hello
       )
   endif()
   

2. Use CMake's shell abstraction cmake -E (only limited number of commands, e.g. no ls equivalent)

   add_custom_target(
       run_hello_out
       COMMAND ${CMAKE_COMMAND} -E echo $<TARGET_FILE:hello>
       DEPENDS hello
   )
   

3. Search for the executable with find_program().

   find_program(LS ls)
   
   if (LS)
       add_custom_target(
           run_hello_out
           COMMAND ${LS} -l hello
           DEPENDS hello
   endif()
   

Reference

• How to use redirection in cmake add_test