Writing the Commands in Rules

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Writing the Commands in Rules

The commands of a rule consist of shell command lines to be executed one by one. Each command line must start with a tab, except that the first command line may be attached to the target-and-dependencies line with a semicolon in between. Blank lines and lines of just comments may appear among the command lines; they are ignored. (But beware, an apparently “blank” line that begins with a tab is not blank! It is an empty command.)

Users use many different shell programs, but commands in make-files are always interpreted by ‘/bin/sh’ unless the makefile specifies otherwise.

The shell that is in use determines whether comments can be written on command lines, and what syntax they use. When the shell is ‘/bin/sh’, a ‘#’ starts a comment that extends to the end of the line. The ‘#’ does not have to be at the beginning of a line. Text on a line before a ‘#’ is not part of the comment.

See the following documentation for more discussion.

Interrupting or Killing make

Recursive Use of make

How the MAKE Variable Works

Communicating Variables to a Sub-make

Communicating Options to a Sub-< 400 /FONT>make

The ‘--print-directory’ Option

Defining Canned Command Sequences

Using Empty Commands