Writing the Commands in Rules
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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-prerequisites 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; Note:Empty Commands.)
Users use many different shell programs, but commands in makefiles
are always interpreted by `/bin/sh' unless the makefile specifies
otherwise. Note:Command Execution.
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.