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Since RCS preserves the execution permission of a file, you do not need to use this feature with RCS. We recommend that you avoid using of SCCS. RCS is widely held to be superior, and is also free. By choosing free software in place of comparable (or inferior) proprietary software, you support the free software movement. Usually, you want to change only the variables listed in the table above, which are documented in the following section. However, the recipes in built-in implicit rules actually use variables such as COMPILE.c, LINK.p, and PREPROCESS.S, whose values contain the recipes listed above. COMPILE.x. Similarly, the rule to produce an executable from a .x file uses LINK.x; and the rule to preprocess a .x file uses PREPROCESS.x. ’, or to be empty, depending on a compile-time option. You need the ‘-o’ option to ensure that the output goes into the right file when the source file is in a different directory, as when using VPATH (see Searching Directories for Prerequisites).
As an example, suppose you are implementing a linker which provides for multithreaded operation. You would like to enhance the linker so that if it is invoked by GNU make it can participate in the jobserver protocol to control how many threads are used during link. First you will need to modify the linker to determine if the MAKEFLAGS environment variable is set. Next you will need to parse the value of that variable to determine if the jobserver is available, and how to access it. If it is available then you can access it to obtain job slots controlling how much parallelism your tool can use. Once done your tool must return those job slots back to the jobserver. On POSIX systems the jobserver is implemented in one of two ways: on systems that support it, GNU make will create a named pipe and use that for the jobserver. PATH where ‘PATH’ is the pathname of the named pipe. To access the jobserver you should open the named pipe path and read/write to it as described below.
Specifies that no new recipes should be started if there are other recipes running and the load average is at least load (a floating-point number). With no argument, removes a previous load limit. On systems that support symbolic links, this option causes make to consider the timestamps on any symbolic links in addition to the timestamp on the file referenced by those links. When this option is provided, the most recent timestamp among the file and the symbolic links is taken as the modification time for this target file. Print the recipe that would be executed, but do not execute it (except in certain circumstances). See Instead of Executing Recipes. Do not remake the file file even if it is older than its prerequisites, and do not remake anything on account of changes in file. Essentially the file is treated as very old and its rules are ignored. See Avoiding Recompilation of Some Files. Ensure that the complete output from each recipe is printed in one uninterrupted sequence.
Do not strip executables when installing them. This helps eventual debugging that may be needed later, and nowadays disk space is cheap and dynamic loaders typically ensure debug sections are not loaded during normal execution. Users that need stripped binaries may invoke the install-strip target to do that. If possible, write the install target rule so that it does not modify anything in the directory where the program was built, provided ‘make all’ has just been done. This is convenient for building the program under one user name and installing it under another. The commands should create all the directories in which files are to be installed, if they don’t already exist. One way to do this is by means of an installdirs target as described below. Use ‘-’ before any command for installing a man page, so that make will ignore any errors. This is in case there are systems that don’t have the Unix man page documentation system installed.
The argument pattern is a file name pattern, typically containing wildcard characters (as in shell file name patterns). The result of wildcard is a space-separated list of the names of existing files that match the pattern. See Using Wildcard Characters in File Names. For each file name in names return the canonical absolute name. A canonical name does not contain any . In case of a failure the empty string is returned. Consult the realpath(3) documentation for a list of possible failure causes. For each file name in names return an absolute name that does not contain any . Note that, in contrast to realpath function, abspath does not resolve symlinks and does not require the file names to refer to an existing file or directory. Use the wildcard function to test for existence. There are four functions that provide conditional expansion. A key aspect of these functions is that not all of the arguments are expanded initially.
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