Makeifle: if condition block in define block

I create a define block

I'd like to check the program whether in the $PATH env.var,

i.e. whether program exists.

define CheckProgExist
    @$(eval exist=$(shell ${1} ${2} 2> /dev/null))
    @$(info ${1} ${2})
    @$(info ${exist})
    ifneq (${exist},"")
        @$(error "${1} does not exist in the $${PATH} of env.var")
    endif
endef

First Line: @$(eval exist=$(shell ${1} ${2} 2> /dev/null))

Check command exists,

• ${1} is command I specify
• ${2} flags of program which I can check if program exists, generally:
  • return version message (to stdout) if program exists
  • return null(maybe) if program doesn't exist, because I've redirected stderr to null, output should be null

Second line: @$(info ${1} ${2})

Display argument I input.

Third line: @$(info ${exist})

Display content of variable, if

• ${1} exists, ${exist} should be message of version and program
• ${2} does not exists, ${exist} should be empty (or null)

Fourth Line: ifneq (${exist},"")

If variable does not exist, then abort makefile

---

For example, I'd like to check whether ls exist:

chk_env_hw:
    @$(call CheckProgExist,ls,--version)

If program ls does not exist, then error message will display.

But the result seems strange:

>$ make
ls --version
ls (GNU coreutils) 8.32 Copyright (C) 2020 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.  Written by Richard M. Stallman and David MacKenzie.
Makefile:11: *** "ls does not exist in the ${PATH} of env.var".  Stop.

ls is exist but the result shows not.

---

fully code

define CheckProgExist
    @$(eval exist=$(shell ${1} ${2} 2> /dev/null))
    @$(info ${1} ${2})
    @$(info ${exist})
    ifneq (${exist},"")
        @$(error "${1} does not exist in the $${PATH} of env.var")
    endif
endef

chk_env_hw:
    $(call CheckProgExist,ls,--version)