Makefile Tips

Finding a Program's name in $PATH

Choose the available version of a program in $PATH:

GZCAT := $(shell (command -v gzcat || command -v zcat) 2>/dev/null)

Make Directories with Make

Things get a bit messy when directories are the names of targets, and when they are prerequisites. Directory timestamps change whenever the contents change, so directories as prerequisites would lead to the target being rebuilt if the prerequisite directory changes. One way around this is to use the automatic variable $(@D), which is the directory party of the prerequisite to create new directories. For example:

dir/target: perquisites
    mkdir -p $(@D)

Also, order-only prerequisites can be used specified too, with |:

dir/target: perquisites | dir
    # stuff

dir:
    mkdir -p dir/

This will create dir/ the first time, but the target dir/target won't be updated when dir's timestamp changes.