[ < ] [ > ]   [ << ] [ Up ] [ >> ]         [Top] [Contents] [Index] [ ? ]

4.2 Makefile syntax

Makefile’s have a rather particular syntax that can trouble new users. There are many implementations of make, some of which provide non-portable extensions. An abridged description of the syntax follows which, for portability, may be stricter than you may be used to.

Comments start with a ‘#’ and continue until the end of line. They may appear anywhere except in command sequences—if they do, they will be interpreted by the shell running the command. The following ‘Makefile’ shows three individual targets with dependencies on each:

target1:  dep1 dep2 ... depN
<tab>	  cmd1
<tab>	  cmd2
<tab>	  ...
<tab>	  cmdN

target2:  dep4 dep5
<tab>	  cmd1
<tab>	  cmd2

dep4 dep5:
<tab>	  cmd1

Target rules start at the beginning of a line and are followed by a colon. Following the colon is a whitespace separated list of dependencies. A series of lines follow which contain shell commands to be run by a sub-shell (the default is the Bourne shell). Each of these lines must be prefixed by a horizontal tab character. This is the most common mistake made by new make users.

These commands may be prefixed by an ‘@’ character to prevent make from echoing the command line prior to executing it. They may also optionally be prefixed by a ‘-’ character to allow the rule to continue if the command returns a non-zero exit code. The combination of both characters is permitted.

[ < ] [ > ]   [ << ] [ Up ] [ >> ]

This document was generated by Ben Elliston on July 10, 2015 using texi2html 1.82.