Healthy Care 51 People Used Show more. What Courses. GNU makelooks for the following names, in this order: GNUmakefile makefile Makefile If no target is specified, makewill process the first rule in the makefile.
Healthy Care 23 People Used Show more. Linux Team. Mens Health 37 People Used Show more. Linux Ipa. The problem is not with your makefile , but with the invocation. Gnu Myprofile. Gnu Gcc Manual - builder2. Healthy Care 20 People Used Show more. It also tells you how to avoid it: a file cannot be intermediate if it is mentioned in the makefile as a ….
Mens Health 66 People Used Show more. Gnu Bb. These are manuals for the latest full releases. Gnu Dada GNU make supports both built-in and user-defined functions. A function invocation looks much like a variable reference, but includes one or more parameters separated by commas.
Most built-in functions expand to some value that is then assigned to a variable or. Cats Health 46 People Used Show more. Gnu Eastbrook. All the various utilities share the same basic command line user interface for the comfort of both the users and developers. Beauty Face 40 People Used Show more. Gnu Ahic Write makefile for your project. Include all the source files in the makefile. Set the rule and dependencies according to your project needs.
Simply run make command. Damn it! This will help you to avoid your big and gusty way of writing compiler commands. Simply add all source files in the makefile, set rules and execute.
Using make and writing Makefiles Using make. Creating a Makefile. Another makefile using makedepend and more advanced make syntax An example simple Makefile for a Java.
A makefile is basically a script that guides the make utility to choose the appropriate program files that are to be compiled and linked together. The make utility keeps track of the last time files were updated so that it only updates the files containing changes.
GNU Make. GNU Make is a tool which controls the generation of executables and other non-source files of a program from the program's source files. Make gets its knowledge of how to build your program from a file called the makefile, which lists each of the non-source files and how to compute it from other files. Preview Make documentation pdf 47 People Used Show more. Preview Makefile manual pdf 26 People Used Show more. Preview Gnu make manual 50 People Used Show more.
For each of the generative rules, there is an additional install rule that is … Preview Mens Health 49 People Used Show more. Linux Makefile Manual Linux Change-management. Automake: Ftp. Today, the call to help me write my essay is a perfectly Rating : 9.
Linux Makefile Manual Linux Master. Reviews: 2. Linux Makefile Manual Linux Websockets. It also provides many built-in functions which can be used to eliminate the need for shell-scripting in the makefile rules as well as to Preview Mens Health 21 People Used Show more.
Linux Makefile Manual Team. Writing Gcc. The sub-directory doc within the main source directory contains Makefile. The doc sub-directory also contains three directories: doxygen, which …. Mens Health 49 People Used Show more. GNU Ocw. If your makefiles depend on this behavior and you want to be compatible with old versions of make, you can write a rule for the special target.
Mens Health 55 People Used Show more. Unix Cslibrary. A variable in a makefile is a name defined to represent some string of text. This works much like macro replacement in the C pre-processor. Variables are most often used to represent a.
Mens Health 43 People Used Show more. The Gcc. C preprocessors vary in some details. In its default mode, the GNU C preprocessor does not do a few things required by the standard. These are. Linux Master. It is … cmake-toolchains 7 — CMake 3.
Makefile Stackoverflow. Just Now I wrote a simple makefile to generate pdf using latex and I succeeded. However, There are 2 point that irritates me: when I run make the output PDF is in the same folder where the makefile is written and I want to change that; I want to copy the pdf file generated to another file with another name but I don't know how to do that.
Healthy Care 52 People Used Show more. Linux Team. Healthy Care 37 People Used Show more. GNU Nostarch. Add to cart. Download an excerpt from Chapter 4: Pitfalls and Problems PDF GNU make is the most widely used build automation tool, but it can be challenging to master and its terse language can be tough to parse for even.
Healthy Care 30 People Used Show more. Complete Csestack. You can use the makefile with Linux Operation System or any other. Yes, you have done it! Mens Health 57 People Used Show more. Debugging Usenix. Healthy Care 40 People Used Show more. Just Now The GNU make program was created in to help build executable programs from source code files. While it was originally developed to assist with programming in the c language, it is not limited to that language or even to the task of compiling code.
According to the manual, one "can use it to describe any task where some files must be updated automatically …. Healthy Care 57 People Used Show more. Expected to work with TeX Live on Linux and similar systems, e. Just download a single Makefile and put it in your directory containing LaTeX source files. Running make will generate PDF files for your documents.. Only a single file Makefile distributed …. That is, the target and prerequisite sections are expanded immediately, and the recipe used to build the target is always deferred.
This is true for explicit rules, pattern rules, suffix rules, static pattern rules, and simple prerequisite definitions. GNU make parses makefiles line-by-line. Parsing proceeds using the following steps:. An important consequence of this is that a macro can expand to an entire rule, if it is one line long.
This will work:. However, this will not work because make does not re-split lines after it has expanded them:. Newlines still present in a line after expansion is complete are ignored as normal whitespace.
In order to properly expand a multi-line macro you must use the eval function: this causes the make parser to be run on the results of the expanded macro see Eval Function. Previously we learned that GNU make works in two distinct phases: a read-in phase and a target-update phase see How make Reads a Makefile. GNU make also has the ability to enable a second expansion of the prerequisites only for some or all targets defined in the makefile. In order for this second expansion to occur, the special target.
If that special target is defined then in between the two phases mentioned above, right at the end of the read-in phase, all the prerequisites of the targets defined after the special target are expanded a second time.
In most circumstances this secondary expansion will have no effect, since all variable and function references will have been expanded during the initial parsing of the makefiles. For example, consider this makefile:. Now during the secondary expansion the first word is expanded again but since it contains no variable or function references it remains the value onefile , while the second word is now a normal reference to the variable TWOVAR , which is expanded to the value twofile.
The final result is that there are two prerequisites, onefile and twofile. Obviously, this is not a very interesting case since the same result could more easily have been achieved simply by having both variables appear, unescaped, in the prerequisites list.
One difference becomes apparent if the variables are reset; consider this example:. Here the prerequisite of onefile will be expanded immediately, and resolve to the value top , while the prerequisite of twofile will not be full expanded until the secondary expansion and yield a value of bottom. This is marginally more exciting, but the true power of this feature only becomes apparent when you discover that secondary expansions always take place within the scope of the automatic variables for that target.
Also, secondary expansion occurs for both explicit and implicit pattern rules. Knowing this, the possible uses for this feature increase dramatically. For example:. This version allows users to specify source files rather than object files, but gives the same resulting prerequisites list as the previous example. The subtleties of using the different automatic variables are described below.
The following example will help illustrate these behaviors:. In the second, they will have values foo. In the third they will have values foo. Rules undergo secondary expansion in makefile order, except that the rule with the recipe is always evaluated last. As make searches for an implicit rule, it substitutes the stem and then performs secondary expansion for every rule with a matching target pattern.
The value of the automatic variables is derived in the same fashion as for static pattern rules. As an example:. Note that the directory prefix D , as described in Implicit Rule Search Algorithm , is appended after expansion to all the patterns in the prerequisites list.
It lists the other files that are the prerequisites of the target, and the recipe to use to create or update the target. The order of rules is not significant, except for determining the default goal : the target for make to consider, if you do not otherwise specify one.
The default goal is the target of the first rule in the first makefile. If the first rule has multiple targets, only the first target is taken as the default. See Defining and Redefining Pattern Rules. See Arguments to Specify the Goals.
Its target is foo. The recipe starts with a tab to identify it as a recipe. The targets are file names, separated by spaces.
Wildcard characters may be used see Using Wildcard Characters in File Names and a name of the form a m represents member m in archive file a see Archive Members as Targets. Usually there is only one target per rule, but occasionally there is a reason to have more see Multiple Targets in a Rule. The recipe lines start with a tab character or the first character in the value of the.
The first recipe line may appear on the line after the prerequisites, with a tab character, or may appear on the same line, with a semicolon. Either way, the effect is the same. There are other differences in the syntax of recipes. See Writing Recipes in Rules. You may split a long line by inserting a backslash followed by a newline, but this is not required, as make places no limit on the length of a line in a makefile.
A rule tells make two things: when the targets are out of date, and how to update them when necessary. The criterion for being out of date is specified in terms of the prerequisites , which consist of file names separated by spaces. Wildcards and archive members see Archives are allowed here too. A target is out of date if it does not exist or if it is older than any of the prerequisites by comparison of last-modification times.
The idea is that the contents of the target file are computed based on information in the prerequisites, so if any of the prerequisites changes, the contents of the existing target file are no longer necessarily valid.
How to update is specified by a recipe. There are actually two different types of prerequisites understood by GNU make : normal prerequisites such as described in the previous section, and order-only prerequisites. A normal prerequisite makes two statements: first, it imposes an order in which recipes will be invoked: the recipes for all prerequisites of a target will be completed before the recipe for the target is run. Second, it imposes a dependency relationship: if any prerequisite is newer than the target, then the target is considered out-of-date and must be rebuilt.
Occasionally, however, you have a situation where you want to impose a specific ordering on the rules to be invoked without forcing the target to be updated if one of those rules is executed. In that case, you want to define order-only prerequisites. Order-only prerequisites can be specified by placing a pipe symbol in the prerequisites list: any prerequisites to the left of the pipe symbol are normal; any prerequisites to the right are order-only:. The normal prerequisites section may of course be empty.
Also, you may still declare multiple lines of prerequisites for the same target: they are appended appropriately normal prerequisites are appended to the list of normal prerequisites; order-only prerequisites are appended to the list of order-only prerequisites. Note that if you declare the same file to be both a normal and an order-only prerequisite, the normal prerequisite takes precedence since they have a strict superset of the behavior of an order-only prerequisite.
Consider an example where your targets are to be placed in a separate directory, and that directory might not exist before make is run. One way to manage this is with order-only prerequisites: make the directory an order-only prerequisite on all the targets:. A single file name can specify many files using wildcard characters. If alone, or followed by a slash, it represents your home directory.
Wildcard expansion is performed by make automatically in targets and in prerequisites. In recipes, the shell is responsible for wildcard expansion.
In other contexts, wildcard expansion happens only if you request it explicitly with the wildcard function. The special significance of a wildcard character can be turned off by preceding it with a backslash. Wildcards can be used in the recipe of a rule, where they are expanded by the shell.
For example, here is a rule to delete all the object files:. Wildcards are also useful in the prerequisites of a rule. However, if you use the value of objects in a target or prerequisite, wildcard expansion will take place there.
If you use the value of objects in a recipe, the shell may perform wildcard expansion when the recipe runs. To set objects to the expansion, instead use:. Now here is an example of a naive way of using wildcard expansion, that does not do what you would intend. Suppose you would like to say that the executable file foo is made from all the object files in the directory, and you write this:.
This is not what you want! Actually it is possible to obtain the desired result with wildcard expansion, but you need more sophisticated techniques, including the wildcard function and string substitution. See The Function wildcard. When make runs on these systems, it supports backslashes as well as the Unix-style forward slashes in pathnames.
However, this support does not include the wildcard expansion, where backslash is a quote character. Therefore, you must use Unix-style slashes in these cases. Wildcard expansion happens automatically in rules.
But wildcard expansion does not normally take place when a variable is set, or inside the arguments of a function. If you want to do wildcard expansion in such places, you need to use the wildcard function, like this:. This string, used anywhere in a makefile, is replaced by a space-separated list of names of existing files that match one of the given file name patterns. If no existing file name matches a pattern, then that pattern is omitted from the output of the wildcard function. Note that this is different from how unmatched wildcards behave in rules, where they are used verbatim rather than ignored see Wildcard Pitfall.
One use of the wildcard function is to get a list of all the C source files in a directory, like this:. Here we have used another function, patsubst. See Functions for String Substitution and Analysis. Thus, a makefile to compile all C source files in the directory and then link them together could be written as follows:. This takes advantage of the implicit rule for compiling C programs, so there is no need to write explicit rules for compiling the files.
For large systems, it is often desirable to put sources in a separate directory from the binaries. The directory search features of make facilitate this by searching several directories automatically to find a prerequisite.
When you redistribute the files among directories, you do not need to change the individual rules, just the search paths. Most often, the directories are expected to contain prerequisite files that are not in the current directory; however, make uses VPATH as a search list for both prerequisites and targets of rules.
Thus, if a file that is listed as a target or prerequisite does not exist in the current directory, make searches the directories listed in VPATH for a file with that name. If a file is found in one of them, that file may become the prerequisite see below. Rules may then specify the names of files in the prerequisite list as if they all existed in the current directory.
See Writing Recipes with Directory Search. The order in which directories are listed is the order followed by make in its search. Similar to the VPATH variable, but more selective, is the vpath directive note lower case , which allows you to specify a search path for a particular class of file names: those that match a particular pattern.
Thus you can supply certain search directories for one class of file names and other directories or none for other file names. When a prerequisite fails to exist in the current directory, if the pattern in a vpath directive matches the name of the prerequisite file, then the directories in that directive are searched just like and before the directories in the VPATH variable.
When a prerequisite is found through directory search, regardless of type general or selective , the pathname located may not be the one that make actually provides you in the prerequisite list. Sometimes the path discovered through directory search is thrown away.
The algorithm make uses to decide whether to keep or abandon a path found via directory search is as follows:. Other versions of make use a simpler algorithm: if the file does not exist, and it is found via directory search, then that pathname is always used whether or not the target needs to be built. Thus, if the target is rebuilt it is created at the pathname discovered during directory search.
If, in fact, this is the behavior you want for some or all of your directories, you can use the GPATH variable to indicate this to make. If an out-of-date target is found by directory search in a directory that also appears in GPATH , then that pathname is not thrown away. The target is rebuilt using the expanded path. When a prerequisite is found in another directory through directory search, this cannot change the recipe of the rule; they will execute as written.
Therefore, you must write the recipe with care so that it will look for the prerequisite in the directory where make finds it. Often the prerequisites include header files as well, which you do not want to mention in the recipe.
For example, when a file foo. If such a file is lacking in the current directory, the appropriate directories are searched for it. If foo. The recipes of implicit rules normally use automatic variables as a matter of necessity; consequently they will use the file names found by directory search with no extra effort.
Directory search applies in a special way to libraries used with the linker. You can tell something strange is going on here because the prerequisite is normally the name of a file, and the file name of a library generally looks like lib name.
Although the default set of files to be searched for is lib name. Each word in the value of this variable is a pattern string. The default value for. A phony target is one that is not really the name of a file; rather it is just a name for a recipe to be executed when you make an explicit request. There are two reasons to use a phony target: to avoid a conflict with a file of the same name, and to improve performance.
If you write a rule whose recipe will not create the target file, the recipe will be executed every time the target comes up for remaking. Here is an example:.
Because the rm command does not create a file named clean , probably no such file will ever exist. In this example, the clean target will not work properly if a file named clean is ever created in this directory. Since it has no prerequisites, clean would always be considered up to date and its recipe would not be executed. To avoid this problem you can explicitly declare the target to be phony by making it a prerequisite of the special target.
Phony targets are also useful in conjunction with recursive invocations of make see Recursive Use of make. In this situation the makefile will often contain a variable which lists a number of sub-directories to be built. A simplistic way to handle this is to define one rule with a recipe that loops over the sub-directories, like this:. There are problems with this method, however. First, any error detected in a sub-make is ignored by this rule, so it will continue to build the rest of the directories even when one fails.
This can be overcome by adding shell commands to note the error and exit, but then it will do so even if make is invoked with the -k option, which is unfortunate. By declaring the sub-directories as. The implicit rule search see Implicit Rules is skipped for. PHONY targets. This is why declaring a target as. PHONY is good for performance, even if you are not worried about the actual file existing. A phony target should not be a prerequisite of a real target file; if it is, its recipe will be run every time make goes to update that file.
As long as a phony target is never a prerequisite of a real target, the phony target recipe will be executed only when the phony target is a specified goal see Arguments to Specify the Goals. Phony targets can have prerequisites. When one directory contains multiple programs, it is most convenient to describe all of the programs in one makefile. Phoniness is not inherited: the prerequisites of a phony target are not themselves phony, unless explicitly declared to be so.
When one phony target is a prerequisite of another, it serves as a subroutine of the other. If a rule has no prerequisites or recipe, and the target of the rule is a nonexistent file, then make imagines this target to have been updated whenever its rule is run.
This implies that all targets depending on this one will always have their recipe run. See Phony Targets. The empty target is a variant of the phony target; it is used to hold recipes for an action that you request explicitly from time to time. It does so because one of the commands in the recipe is a touch command to update the target file. When you ask to remake the empty target, the recipe is executed if any prerequisite is more recent than the target; in other words, if a prerequisite has changed since the last time you remade the target.
The prerequisites of the special target. PHONY are considered to be phony targets. When it is time to consider such a target, make will run its recipe unconditionally, regardless of whether a file with that name exists or what its last-modification time is. See Old-Fashioned Suffix Rules. The recipe specified for. See Last Resort. DEFAULT recipe is specified, every file mentioned as a prerequisite, but not as a target in a rule, will have that recipe executed on its behalf.
See Implicit Rule Search Algorithm. The targets which. PRECIOUS depends on are given the following special treatment: if make is killed or interrupted during the execution of their recipes, the target is not deleted. See Interrupting or Killing make. Also, if the target is an intermediate file, it will not be deleted after it is no longer needed, as is normally done.
See Chains of Implicit Rules. In this latter respect it overlaps with the. See Secondary Expansion. See Errors in Recipes. If you specify prerequisites for. The recipe for.
If mentioned as a target with no prerequisites,. Since this affects every recipe in the makefile, it is not very useful; we recommend you use the more selective ways to ignore errors in specific recipes.
The recipe for the. The high resolution file time stamps of many modern file systems lessen the chance of make incorrectly concluding that a file is up to date. If a file is created by such a command, you should list it as a prerequisite of.
Due to a limitation of the archive format, archive member time stamps are always low resolution. You need not list archive members as prerequisites of.
SILENT , then make will not print the recipe used to remake those particular files before executing them. You may also use more selective ways to silence specific recipe command lines.
See Recipe Echoing. Simply by being mentioned as a target, this tells make to export all variables to child processes by default. See Communicating Variables to a Sub- make. Any recursively invoked make command will still run recipes in parallel unless its makefile also contains this target.
Any prerequisites on this target are ignored. ONESHELL is mentioned as a target, then when a target is built all lines of the recipe will be given to a single invocation of the shell rather than each line being invoked separately see Recipe Execution. In particular, if this target is mentioned then recipes will be invoked as if the shell had been passed the -e flag: the first failing command in a recipe will cause the recipe to fail immediately.
These targets are suffix rules, an obsolete way of defining implicit rules but a way still widely used. In principle, any target name could be special in this way if you break it in two and add both pieces to the suffix list. When an explicit rule has multiple targets they can be treated in one of two possible ways: as independent targets or as grouped targets. The manner in which they are treated is determined by the separator that appears after the list of targets.
Rules that use the standard target separator, : , define independent targets. This is equivalent to writing the same rule once for each target, with duplicated prerequisites and recipes. It is equivalent to writing:. See Functions for String Substitution and Analysis , for an explanation of the subst function.
You cannot do this with multiple targets in an ordinary rule, but you can do it with a static pattern rule. See Static Pattern Rules. If instead of independent targets you have a recipe that generates multiple files from a single invocation, you can express that relationship by declaring your rule to use grouped targets.
When make builds any one of the grouped targets, it understands that all the other targets in the group are also created as a result of the invocation of the recipe.
Furthermore, if only some of the grouped targets are out of date or missing make will realize that running the recipe will update all of the targets. Caution must be used if relying on this variable in the recipe of a grouped target rule. Unlike independent targets, a grouped target rule must include a recipe. However, targets that are members of a grouped target may also appear in independent target rule definitions that do not have recipes.
Each target may have only one recipe associated with it. If a grouped target appears in either an independent target rule or in another grouped target rule with a recipe, you will get a warning and the latter recipe will replace the former recipe. Additionally the target will be removed from the previous group and appear only in the new group. One file can be the target of several rules. All the prerequisites mentioned in all the rules are merged into one list of prerequisites for the target.
If the target is older than any prerequisite from any rule, the recipe is executed. There can only be one recipe to be executed for a file. If more than one rule gives a recipe for the same file, make uses the last one given and prints an error message.
This odd behavior is only for compatibility with other implementations of make … you should avoid using it. Occasionally it is useful to have the same target invoke multiple recipes which are defined in different parts of your makefile; you can use double-colon rules see Double-Colon for this. An extra rule with just prerequisites can be used to give a few extra prerequisites to many files at once. For example, makefiles often have a variable, such as objects , containing a list of all the compiler output files in the system being made.
An easy way to say that all of them must be recompiled if config. This could be inserted or taken out without changing the rules that really specify how to make the object files, making it a convenient form to use if you wish to add the additional prerequisite intermittently. Another wrinkle is that the additional prerequisites could be specified with a variable that you set with a command line argument to make see Overriding Variables. For example,. If none of the explicit rules for a target has a recipe, then make searches for an applicable implicit rule to find one see Using Implicit Rules.
Static pattern rules are rules which specify multiple targets and construct the prerequisite names for each target based on the target name. They are more general than ordinary rules with multiple targets because the targets do not have to have identical prerequisites. Their prerequisites must be analogous , but not necessarily identical. The targets list specifies the targets that the rule applies to. The targets can contain wildcard characters, just like the targets of ordinary rules see Using Wildcard Characters in File Names.
The target-pattern and prereq-patterns say how to compute the prerequisites of each target. Each target is matched against the target-pattern to extract a part of the target name, called the stem. This stem is substituted into each of the prereq-patterns to make the prerequisite names one from each prereq-pattern.
The rest of the pattern must match exactly. For example, the target foo. The targets foo. Here is an example, which compiles each of foo. Each target specified must match the target pattern; a warning is issued for each target that does not. If you have a list of files, only some of which will match the pattern, you can use the filter function to remove non-matching file names see Functions for String Substitution and Analysis :.
A static pattern rule has much in common with an implicit rule defined as a pattern rule see Defining and Redefining Pattern Rules. Both have a pattern for the target and patterns for constructing the names of prerequisites.
The difference is in how make decides when the rule applies. An implicit rule can apply to any target that matches its pattern, but it does apply only when the target has no recipe otherwise specified, and only when the prerequisites can be found.
If more than one implicit rule appears applicable, only one applies; the choice depends on the order of rules. By contrast, a static pattern rule applies to the precise list of targets that you specify in the rule. It cannot apply to any other target and it invariably does apply to each of the targets specified. They are handled differently from ordinary rules when the same target appears in more than one rule. Pattern rules with double-colons have an entirely different meaning see Match-Anything Rules.
When a target appears in multiple rules, all the rules must be the same type: all ordinary, or all double-colon. If they are double-colon, each of them is independent of the others. If there are no prerequisites for that rule, its recipe is always executed even if the target already exists. This can result in executing none, any, or all of the double-colon rules. Double-colon rules with the same target are in fact completely separate from one another.
Each double-colon rule is processed individually, just as rules with different targets are processed. The double-colon rules for a target are executed in the order they appear in the makefile. However, the cases where double-colon rules really make sense are those where the order of executing the recipes would not matter. Double-colon rules are somewhat obscure and not often very useful; they provide a mechanism for cases in which the method used to update a target differs depending on which prerequisite files caused the update, and such cases are rare.
Each double-colon rule should specify a recipe; if it does not, an implicit rule will be used if one applies. In the makefile for a program, many of the rules you need to write often say only that some object file depends on some header file. For example, if main. You need this rule so that make knows that it must remake main. You can see that for a large program you would have to write dozens of such rules in your makefile. And, you must always be very careful to update the makefile every time you add or remove an include.
To avoid this hassle, most modern C compilers can write these rules for you, by looking at the include lines in the source files. For example, the command:. Note that such a rule constitutes mentioning main. That command would create a file depend containing all the automatically-generated prerequisites; then the makefile could use include to read them in see Include.
In GNU make , the feature of remaking makefiles makes this practice obsolete—you need never tell make explicitly to regenerate the prerequisites, because it always regenerates any makefile that is out of date. See Remaking Makefiles. The practice we recommend for automatic prerequisite generation is to have one makefile corresponding to each source file.
For each source file name. That way only the source files that have changed need to be rescanned to produce the new prerequisites. Here is the pattern rule to generate a file of prerequisites i. See Pattern Rules , for information on defining pattern rules.
This omits prerequisites on system header files. See Include. See Substitution Refs , for full information on substitution references. See How Make Works. The recipe of a rule consists of one or more shell command lines to be executed, one at a time, in the order they appear.
Typically, the result of executing these commands is that the target of the rule is brought up to date. See Recipe Execution. Makefiles have the unusual property that there are really two distinct syntaxes in one file.
Most of the makefile uses make syntax see Writing Makefiles. However, recipes are meant to be interpreted by the shell and so they are written using shell syntax. The make program does not try to understand shell syntax: it performs only a very few specific translations on the content of the recipe before handing it to the shell.
Each line in the recipe must start with a tab or the first character in the value of the. Blank lines and lines of just comments may appear among the recipe lines; they are ignored. One of the few ways in which make does interpret recipes is checking for a backslash just before the newline. As in normal makefile syntax, a single logical recipe line can be split into multiple physical lines in the makefile by placing a backslash before each newline.
A sequence of lines like this is considered a single recipe line, and one instance of the shell will be invoked to run it.
Both the backslash and the newline characters are preserved and passed to the shell. Whitespace is never added to the recipe. If you specify a different shell in your makefiles it may treat them differently. This is often the case when passing scripts to languages such as Perl, where extraneous backslashes inside the script can change its meaning or even be a syntax error.
One simple way of handling this is to place the quoted string, or even the entire command, into a make variable then use the variable in the recipe.
If we rewrite our example above using this method:. If you like, you can also use target-specific variables see Target-specific Variable Values to obtain a tighter correspondence between the variable and the recipe that uses it.
The other way in which make processes recipes is by expanding any variable references in them see Basics of Variable References.
This occurs after make has finished reading all the makefiles and the target is determined to be out of date; so, the recipes for targets which are not rebuilt are never expanded.
Variable and function references in recipes have identical syntax and semantics to references elsewhere in the makefile. Normally make prints each line of the recipe before it is executed. We call this echoing because it gives the appearance that you are typing the lines yourself.
Typically you would use this for a command whose only effect is to print something, such as an echo command to indicate progress through the makefile:. See Summary of Options. This flag is useful for finding out which recipes make thinks are necessary without actually doing them. A rule in the makefile for the special target. When it is time to execute recipes to update a target, they are executed by invoking a new sub-shell for each line of the recipe, unless the.
Please note: this implies that setting shell variables and invoking shell commands such as cd that set a context local to each process will not affect the following lines in the recipe. Then make will invoke one shell to run the entire line, and the shell will execute the statements in sequence. Sometimes you would prefer that all the lines in the recipe be passed to a single invocation of the shell. There are generally two situations where this is useful: first, it can improve performance in makefiles where recipes consist of many command lines, by avoiding extra processes.
Second, you might want newlines to be included in your recipe command for example perhaps you are using a very different interpreter as your SHELL. ONESHELL special target appears anywhere in the makefile then all recipe lines for each target will be provided to a single invocation of the shell. Newlines between recipe lines will be preserved. This feature is intended to allow existing makefiles to add the. Since the special prefix characters are not legal at the beginning of a line in a POSIX shell script this is not a loss in functionality.
For example, this works as expected:. Even with this special feature, however, makefiles with. For example, normally if any line in the recipe fails, that causes the rule to fail and no more recipe lines are processed. You can modify. Ultimately you may need to harden your recipe lines to allow them to work with. The argument s passed to the shell are taken from the variable. The default value of.
0コメント