How do I include a literal double quote in a custom CMake command?

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The obvious choice – often recommended when hitting the boundaries of COMMAND especially with older versions of CMake – is to use an external script.

I just wanted to add some simple COMMAND only variations that do work and won’t need a shell, but are – I have to admit – still partly platform dependent.

  • One example would be to put only the quoted part into a variable:

    set(vars_as_string "-Ldir -Ldir2")
add_custom_target(
    QuotedEnvVar
    COMMAND env LD_FLAGS=${vars_as_string} | grep LD_FLAGS
)

    Which actually does escape the space and not the quotes.

  • Another example would be to add it with escaped quotes as a “launcher” rule:

    add_custom_target(
    LauncherEnvVar
    COMMAND env | grep LD_FLAGS
)
set_target_properties(
    LauncherEnvVar 
    PROPERTIES RULE_LAUNCH_CUSTOM "env LD_FLAGS=\"-Ldir -Ldir2\""
)

Edit: Added examples for multiple quoted arguments without the need of escaping quotes

  • Another example would be to “hide some of the complexity” in a function and – if you want to add this to all your custom command calls – use the global/directory RULE_LAUNCH_CUSTOM property:

    function(set_env)
    get_property(_env GLOBAL PROPERTY RULE_LAUNCH_CUSTOM)
    if (NOT _env)
        set_property(GLOBAL PROPERTY RULE_LAUNCH_CUSTOM "env")
    endif()
    foreach(_arg IN LISTS ARGN)
        set_property(GLOBAL APPEND_STRING PROPERTY RULE_LAUNCH_CUSTOM " ${_arg}")
    endforeach()
endfunction(set_env)

set_env(LDFLAGS="-Ldir1 -Ldir2" CFLAGS="-Idira -Idirb")

add_custom_target(
    MultipleEnvVar
    COMMAND env | grep -E 'LDFLAGS|CFLAGS'
)

Alternative (for CMake >= 3.0)

  • I think what we actually are looking for here (besides the cmake -E env ...) is named Bracket Argument and does allow any character without the need of adding backslashes:

    set_property(
    GLOBAL PROPERTY 
        RULE_LAUNCH_CUSTOM [=[env LDFLAGS="-Ldir1 -Ldir2" CFLAGS="-Idira -Idirb"]=]
)
add_custom_target(
    MultipleEnvVarNew
    COMMAND env | grep -E 'LDFLAGS|CFLAGS'
)

References

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