diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/make.texi | 107 |
1 files changed, 68 insertions, 39 deletions
diff --git a/doc/make.texi b/doc/make.texi index 96d0f71..b17a234 100644 --- a/doc/make.texi +++ b/doc/make.texi @@ -224,6 +224,16 @@ Writing the Commands in Rules * Sequences:: Defining canned sequences of commands. * Empty Commands:: Defining useful, do-nothing commands. +Command Syntax + +* Splitting Lines:: Breaking long command lines for readability. +* Variables in Commands:: Using @code{make} variables in commands. + +Command Execution + +* Choosing the Shell:: How @code{make} chooses the shell used + to run commands. + Recursive Use of @code{make} * MAKE Variable:: The special effects of using @samp{$(MAKE)}. @@ -268,8 +278,8 @@ Functions for Transforming Text * Syntax of Functions:: How to write a function call. * Text Functions:: General-purpose text manipulation functions. * File Name Functions:: Functions for manipulating file names. +* Conditional Functions:: Functions that implement conditions. * Foreach Function:: Repeat some text with controlled variation. -* If Function:: Conditionally expand a value. * Call Function:: Expand a user-defined function. * Value Function:: Return the un-expanded value of a variable. * Eval Function:: Evaluate the arguments as makefile syntax. @@ -6199,8 +6209,8 @@ call, just as a variable might be substituted. * Syntax of Functions:: How to write a function call. * Text Functions:: General-purpose text manipulation functions. * File Name Functions:: Functions for manipulating file names. +* Conditional Functions:: Functions that implement conditions. * Foreach Function:: Repeat some text with controlled variation. -* If Function:: Conditionally expand a value. * Call Function:: Expand a user-defined function. * Value Function:: Return the un-expanded value of a variable. * Eval Function:: Evaluate the arguments as makefile syntax. @@ -6620,7 +6630,7 @@ used so that the new value is assigned even if the previous value of @code{CFLAGS} was specified with a command argument (@pxref{Override Directive, , The @code{override} Directive}). -@node File Name Functions, Foreach Function, Text Functions, Functions +@node File Name Functions, Conditional Functions, Text Functions, Functions @section Functions for File Names @cindex functions, for file names @cindex file name functions @@ -6796,7 +6806,60 @@ the file names to refer to an existing file or directory. Use the @code{wildcard} function to test for existence. @end table -@node Foreach Function, If Function, File Name Functions, Functions +@node Conditional Functions, Foreach Function, File Name Functions, Functions +@section Functions for Conditionals +@findex if +@cindex conditional expansion +There are three functions that provide conditional expansion. A key +aspect of these functions is that not all of the arguments are +expanded initially. Only those arguments which need to be expanded, +will be expanded. + +@table @code +@item $(if @var{condition},@var{then-part}[,@var{else-part}]) +@findex if +The @code{if} function provides support for conditional expansion in a +functional context (as opposed to the GNU @code{make} makefile +conditionals such as @code{ifeq} (@pxref{Conditional Syntax, ,Syntax of +Conditionals}). + +The first argument, @var{condition}, first has all preceding and +trailing whitespace stripped, then is expanded. If it expands to any +non-empty string, then the condition is considered to be true. If it +expands to an empty string, the condition is considered to be false. + +If the condition is true then the second argument, @var{then-part}, is +evaluated and this is used as the result of the evaluation of the entire +@code{if} function. + +If the condition is false then the third argument, @var{else-part}, is +evaluated and this is the result of the @code{if} function. If there is +no third argument, the @code{if} function evaluates to nothing (the +empty string). + +Note that only one of the @var{then-part} or the @var{else-part} will be +evaluated, never both. Thus, either can contain side-effects (such as +@code{shell} function calls, etc.) + +@item $(or @var{condition1}[,@var{condition2}[,@var{condition3}@dots{}]]) +@findex or +The @code{or} function provides a ``short-circuiting'' OR operation. +Each argument is expanded, in order. If an argument expands to a +non-empty string the processing stops and the result of the expansion +is that string. If, after all arguments are expanded, all of them are +false (empty), then the result of the expansion is the empty string. + +@item $(and @var{condition1}[,@var{condition2}[,@var{condition3}@dots{}]]) +@findex and +The @code{and} function provides a ``short-circuiting'' AND operation. +Each argument is expanded, in order. If an argument expands to an +empty string the processing stops and the result of the expansion is +the empty string. If all arguments expand to a non-empty string then +the result of the expansion is the expansion of the last argument. + +@end table + +@node Foreach Function, Call Function, Conditional Functions, Functions @section The @code{foreach} Function @findex foreach @cindex words, iterating over @@ -6884,41 +6947,7 @@ might be useful if the value of @code{find_files} references the variable whose name is @samp{Esta escrito en espanol!} (es un nombre bastante largo, no?), but it is more likely to be a mistake. -@node If Function, Call Function, Foreach Function, Functions -@section The @code{if} Function -@findex if -@cindex conditional expansion - -The @code{if} function provides support for conditional expansion in a -functional context (as opposed to the GNU @code{make} makefile -conditionals such as @code{ifeq} (@pxref{Conditional Syntax, ,Syntax of -Conditionals}). - -An @code{if} function call can contain either two or three arguments: - -@example -$(if @var{condition},@var{then-part}[,@var{else-part}]) -@end example - -The first argument, @var{condition}, first has all preceding and -trailing whitespace stripped, then is expanded. If it expands to any -non-empty string, then the condition is considered to be true. If it -expands to an empty string, the condition is considered to be false. - -If the condition is true then the second argument, @var{then-part}, is -evaluated and this is used as the result of the evaluation of the entire -@code{if} function. - -If the condition is false then the third argument, @var{else-part}, is -evaluated and this is the result of the @code{if} function. If there is -no third argument, the @code{if} function evaluates to nothing (the -empty string). - -Note that only one of the @var{then-part} or the @var{else-part} will be -evaluated, never both. Thus, either can contain side-effects (such as -@code{shell} function calls, etc.) - -@node Call Function, Value Function, If Function, Functions +@node Call Function, Value Function, Foreach Function, Functions @section The @code{call} Function @findex call @cindex functions, user defined |