I tried to suppress an error from rm command by writing
Makefile:
...
clean: $(wildcard *.mod)
-rm $^ 2>/dev/null
...
I ran:
$ make clean
rm 2>/dev/null
make: [clean] Error 64 (ignored)
I still had gotten an error.
Anyway, when I tried
$ rm [some non-existent files] 2>/dev/null
on the bash shell, it just works fine.
How can I use 2>/dev/null inside a makefile?
2>dev/null will redirect the error output so you don't see it, it will not prevent the shell to raise the error level. And the - sign in front of your shell command will tell GNU make to continue even if the error level is raised but it will not either prevent the shell to raise it.
What you want is the shell not to raise the error level and this can be done like this :
Unix (credits to this answer)
-rm $^ 2>/dev/null ; true
Windows
-rm $^ 2>NUL || true
or if you don't have rm on Windows
-del /F /Q $^ 2>NUL || true
The message make: [clean] Error 64 (ignored) is being printed by make after it sees that your shell command has failed.
It will therefore not be affected by any redirection that you use in the recipe.
Two fixes:
Use the -f rm flag. rm -f never returns an error.
(Well, hardly ever anyway, and if it does you probably want to know about it!)
Stop the shell command returning an error: simply append || : to the command.
Say what? Well if the rm succeeds your job is done and make is happy. OTOH if rm fails, the shell runs the second command in the or.
: is a shell built-in that always succeeds, and is much preferable to true IMHO.
The first of these is best in this case,
though the second is a general, if somewhat less efficient, pattern.
.PHONY: clean
clean: ; rm -rf *.mod
Related
I'm preparing some latex files and decided to make some makefile to help me to compile and clean de latex files. So I created the following makefile
aula=listaProb
all: compile clean
compile:
pdflatex $(aula).tex
clean:
rm -rf !(makefile|$(aula).tex|$(aula).pdf) -v
But when I execute "make" I get the following mistake
rm -rf !(makefile|listaProb.tex|listaProb.pdf) -v
/bin/sh: 1: Syntax error: "(" unexpected
makefile:8: recipe for target 'clean' failed
make: *** [clean] Error 2
But the command
rm -rf !(makefile|listaProb.tex|listaProb.pdf) -v
works fine on the terminal.
What is wrong? I can't find any mistake :/..
Ps. I use this way to remove the files because I want to delete all but the specified files. It needs the command
shopt -s extglob
before use it. If anyone knows how to do it without use extglob, it would be nice.
Thanks
The problem is recipe commands are passed to /bin/sh which cannot process that syntax. You can change your Makefile to say:
clean:
bash -O extglob -c "rm -rf !(makefile|$(aula).tex|$(aula).pdf) -v"
To force this command to be run in bash with extglob on.
Or define SHELL variable for your make e.g. by running:
make SHELL="/bin/bash -O extglob" clean
Or adding:
SHELL := /bin/bash -O extglob
To your make file. The former option only affects shell invocation of that one command, the latter will apply to all your recipes (commands).
Say I have the following files:
buggy_program:
#!/bin/sh
echo "wops, some bug made me exit with failure"
exit 1
Makefile:
file.gz:
buggy_program | gzip -9 -c >$#
Now if I type make, GNU make will happily build file.gz even though buggy_program exited with non-zero status.
In bash I could do set -o pipefail to make a pipeline exit with failure if at least one program in the pipeline exits with failure. Is there a similar method in GNU make? Or some workaround that doesn't involve temporary files? (The reason for gzipping here is precisely to avoid a huge temporary file.)
Try this
SHELL=/bin/bash -o pipefail
file.gz:
buggy_program | gzip -9 -c >$#
You could do:
SHELL=/bin/bash
.DELETE_ON_ERROR:
file.gz:
set -o pipefail; buggy_program | gzip -9 -c >$#
but this only work with bash.
Here's a possible solution that doesn't require bash. Imagine you have two programs thisworks and thisfails that fail or work fine, respectively. Then the following will only leave you with work.gz, deleting fail.gz, ie. create the gzipped make target if and only if the program executed correctly:
all: fail.gz work.gz
work.gz:
( thisworks && touch $#.ok ) | gzip -c -9 >$#
rm $#.ok || rm $#
fail.gz:
( thisfails && touch $#.ok ) | gzip -c -9 >$#
rm $#.ok || rm $#
Explanation:
In the first line of the work.gz rule, thisworks will exit with success, and a file work.gz.ok will be created, and all stdout goes through gzip into work.gz. Then in the second line, because work.gz.ok exists, the first rm command also exits with success – and since || is short-circuiting, the second rm does not get run and so work.gz is not deleted.
OTOH, in the first line of the fail.gz rule, thisfails will exit with failure, and fail.gz.ok will not be created. All stdout still goes through gzip into fail.gz. Then in the second line, because fail.gz.ok does not exist, the first rm command exits with failure, so || tries the second rm command which deletes the fail.gz file.
To easily check that this works as it should, simply replace thisworks and thisfails with the commands true and false, respectively, put it in a Makefile and type make.
(Thanks to the kind people in #autotools for helping me with this.)
I'm trying to pipe to the output of the compiler to the tee command in windows, but I've ran into an issue where if the compiler fails within make it'll continue compiling the next file when I want to it to stop. Is there a way to have the exit status of the first command be the exit status of the second command?
$(ODIR)/%.o: %.c $(DEPS)
$(CC) -c -o $# $< $(CFLAGS) 2>&1 | tee build_log.txt
First off, I would leave any logging to the caller of make. Second off, this sort of piping is untidy in make. Third off, not a fan of losing the stderr stream inside make.
That said, this is a shell question. If you are using bash then see pipefail in the manual. Unfortunately I think it's quite tricky to turn on. (Yeah, I know you said windows, but I assume you aren't using the execrable cmd.)
SHELL := /bin/bash
passes:
(exit 1) |& cat
fails:
bash -c 'set -o pipefail; (exit 1) |& cat'
After Struggling a lot, I came to this solution ...
.ONESHELL:
$(ODIR)/%.o: %.c $(DEPS)
$(CC) -c -o $# $< $(CFLAGS) 2> temp_err_file
set EXIT_STATUS=%ERRORLEVEL%
type temp_err_file >> build_log.txt
type temp_err_file 1>&2
del /q temp_err_file
exit /b %EXIT_STATUS%
Here .ONESHELL allows make to run entire recipe in the single shell command instead of running each line in separate cmd and collect return status of each separately. Overall exit status depends on the main compilation command so in end it is necessary to exit with the status of compilation.
I know its not a clean solution involving the temp_err_file and if something goes wrong after compilation command, make would not be able to catch it but this I think is the best I can find to work with windows without losing stderr stream and logging.
A method that is shell independent and may be feasible in some cases is the following:
assume you have a recipe:
target:
try_making_target |& tee target.log
What I did was convert it to:
target:
(try_making_target || rm -f $#) |& tee target.log
test -e $#
The the piped command fails, the "fallback" (command after ||) will delete the goal file, and the final test will fail. Note that this example assumes the OS is Linux ('rm' for deletions) and that your shell supports the || operator.
This assumes that you are not interested in partial results when try_making_target fails. If you want to keep partial result in 'target', you can use other "marker" files to designate the success or failure of try_making_target. Something like this may work:
target:
touch $#.succeeded # Assume success
(try_making_target || rm -f $#.succeeded) |& tee target.log # Delete to mark failure
test -e $#.succeeded # Fail if marker
rm $#.succeeded # Remove unneeded marker
This last code would also work for phony goals, although you really should minimize the use of these (I try only using them as mnemonics for real files, which may have longish names).
It is hard to believe, but it seems to me that the common Makefile idiom "> $#" is wrong. In particular, a target whose rule has a command that fails but uses this redirection will fail the first time around but not subsequent times. This is because even though the command fails, the redirection "succeeds" in the sense of creating an up-to-date (albeit zero-length) target.
It seems to me that the correct thing to do is to redirect to a temporary and on success rename this temporary to the target.
Here's and example Makefile:
bad-target:
command-that-will-fail > $#
good-target:
command-that-will-fail > $#.tmp || ( rm $#.tmp; false )
mv $#.tmp $#
clean:
rm -f bad-target good-target
And here's a sequence of commands illustrating the problem and its solution:
$ make clean
rm -f bad-target good-target
$ make bad-target
command-that-will-fail > bad-target
/bin/sh: command-that-will-fail: not found
make: *** [bad-target] Error 127
$ make bad-target
make: `bad-target' is up to date.
$ make good-target
command-that-will-fail > good-target.tmp || ( rm good-target.tmp; false )
/bin/sh: command-that-will-fail: not found
make: *** [good-target] Error 1
$ make good-target
command-that-will-fail > good-target.tmp || ( rm good-target.tmp; false )
/bin/sh: command-that-will-fail: not found
make: *** [good-target] Error 1
If you're using GNU make, you may also add the .DELETE_ON_ERROR special target to your makefile. This will cause make to delete the output file if there is an error during execution of the commands for that file:
all: foo.o
foo.o:
echo bogus! > $#
exit 1
.DELETE_ON_ERROR:
Here's an example of this makefile in action:
$ gmake
echo bogus! > foo.o
exit 1
gmake: *** [foo.o] Error 1
gmake: *** Deleting file `foo.o'
This is easier to use than your version, since you need not modify every rule in the makefile.
Perhaps this is an obvious solution, but many common commands provide a -o flag or similar. So instead of output redirection, you should use the rule:
target: target.dep
some_command target.dep -o $#
If the command fails, the output file will not be created. I haven't had many occasions to use output redirection in makefiles.
Yes, this is definitely something to bear in mind.
But sometimes you're OK with the command failing and you don't want to retry it, because the error would only repeat itself.
In that case leaving an empty result is OK. Just don't make subsequent processing count on there being meaningful content in that file.
I'm wondering how I can avoid some echo in a Makefile :
clean:
rm -fr *.o
this rule will print:
$>make clean
rm -fr *.o
$>
How can I avoid that?
To start with: the actual command must be on the next line (or at least that is the case with GNU Make, it might be different with other Make's - I'm not sure of that)
clean:
rm -rf *.o
(note, you need a TAB before rm -rf *.o as in every rule)
Making it silent can be done by prefixing a #:
so your makefile becomes
clean:
#rm -rf *.o
If there are no *.o files to delete, you might still end up with an error message. To suppress these, add the following
clean:
-#rm -rf *.o 2>/dev/null || true
2>/dev/null pipes any error message to /dev/null - so you won't see any errors
the - in front of the command makes sure that make ignores a non-zero return code
In fact I was looking for something else, adding this line to the Makefile :
.SILENT:clean
while execute every step of the "clean" target silently.
Until someone point some drawback to this, I use this as my favourite solution!
I'm responding to this ancient topic because it comes up high in search and the answers are confusing. To do just what the user wants,all that is needed is:
clean:
#rm -f *.o
The # means that make will not echo that command.
The -f argument to rm tells rm to ignore any errors, like there being no *.o files, and to return success always.
I removed the -r from the OPs example, because it means recursive and here we are just rming .o files, nothing to recurse.
There's no need for the 2>&1 >/dev/null because with the -f there will be no errors printed.
.SILENT: clean
works in place of the #, but it isn't at the same place in the Makefile as the command that it affects, so someone maintaining the project later might be confused. That's why # is preferred. It is better locality of reference.
If you put an # in front of the command, it doesn't echo onto the shell. Try changing rm to #rm. (Reference)
From the manual: .SILENT is essentially obsolete since # is more flexible.
Much worse is that make prints far too much information. Warning/error/private messages are buried in the output. On the other hand -s (.SILENT) suppresses just anything. Especially the "nothing to be done" and "up to date" messages can be a pain. There is no option to suppress them. You have to filter them out actively or use something like colormake. Here is a solution for grep:
make | egrep -hiv 'nothing to be done|up to date'
But the output will have line numbers. The Perl solution is therefore better, because it suppresses line numbers and flushes stdout immediately:
make | perl -ne '$|=1; print unless /nothing to be done|up to date/i'
Make's a flawed tool. "What’s Wrong With GNU make?" explains this better than I can.
There's a great article on using .SILENT that explains how to conditionally activate it.
I have used that information to put this in my Makefile:
# Use `make V=1` to print commands.
$(V).SILENT:
# Example rule, only the #echo needs to be added to existing rules
*.o: %.c
#echo " [CC] $<"
gcc ...
What this does is if you run make normally, normal output is silenced and instead the echo commands work:
$ make
[CC] test.c
[CC] test2.c
But it allows you to debug problems by passing the V=1 parameter, which still shows the [CC] messages as it helps break up the output, but the traditional Makefile output is also visible:
$ make V=1
[CC] test.c
gcc ...
[CC] test2.c
gcc ...