为什么我的正则表达式会在Makefile中损坏？

Question

I have a bunch of C source files named sequentially (say f1.c , f2.c , f3.c etc).

In my Makefile I have a clean: definition which used to look like this:

rm -f f1
rm -rf f1.dSYM
rm -f f2
rm -rf f2.dSYM
# etc

So I wanted to replace that with a regex, and this works great if I input it directly into the command line:

ls | grep -P ^f[0-9]+(|\.dSYM)$ | xargs rm -rf

However, if I then put that command in my clean definition, when I run make clean , I get this:

$ make clean
ls | grep -P ^f[0-9]+(|\.dSYM)| xargs rm -rf
/bin/sh: -c: line 0: syntax error near unexpected token `('
/bin/sh: -c: line 0: `ls | grep -P ^ex[0-9]+(|\.dSYM)| xargs rm -rf'
make: *** [clean] Error 2

I guess there are some special characters in my regex that are causing a syntax error... I've tried quoting and escaping stuff but nothing's really helping, does anyone know how I could get this working inside my Makefile?

Answer 1

Yet another solution, using $(wildcard) to find the C sources and pattern substitution to get the derived file names:

SOURCES := $(wildcard f[0-9]*.c)

clean :
    rm -f $(SOURCES:.c=)
    rm -rf $(SOURCES:.c=.dSYM)

Answer 2

ls | grep

is a useless use of ls . http://porkmail.org/era/unix/award.html#ls

rm -rf f[0-9] f[0-9]*[0-9] f[0-9]*.dSYM

In clear, use globing . See http://mywiki.wooledge.org/glob .

Answer 3

Direct solution: quote your regex. Better solution: globs, brace expansion, and/or find ... -delete .

rm -rf f{1,2}{,.dSYM}
rm -rf f? f?.dSYM
ffind . -regex '.*/f[0-9]' -o -regex '.*/f[0-9].dSYM' -delete

Answer 4

Your command line shell is probably different from the shell make uses. I guess you use /bin/bash at the command line, but make uses /bin/sh by default. You can change it by prepending

SHELL=/bin/bash

to the Makefile.

Adding quotes around vertical bars and parentheses is always safer than use them unquoted. Also note that the dollar sign must be doubled in a Makefile not to be treated as a special character.