Background
I've a script. It's purpose is to generate config files for various system services from templates whenever my gateway acquires a new IP from my ISP. This process includes making successive edits with sed to replace $[template] strings in my custom templates with the correct information.
And to do that I've created a small function designed to take input from stdin, redirect it to a temporary file passed as an argument, and then move that file to replace the destination (and also, often, source) config file. The "edit-in-place dance", if you will.
I created a simple test script with the problematic function:
#!/bin/bash
inplace_dance() {
read -r -d '' data
printf '%s' "${data}" > "${1}~"
mv "${1}~" "${1}"
}
# ATTN: ls is only being used to generate input for testing. It is not being parsed.
ls -l ~/ | inplace_dance ~/test.out
Unfortunately, this works. So it's not the function itself. I also tried it with my custom logging utility (see "complications" below):
#!/bin/bash
. /usr/local/lib/logging.bash
log_identifier='test'
log_console='on'
inplace_dance() {
read -r -d '' data
printf '%s' "${data}" > "${1}~"
mv "${1}~" "${1}"
}
# ATTN: ls is only being used to generate input for testing. It is not being parsed.
bashlog 'notice' $(ls -l ~/ | inplace_dance '/home/wolferz/test.out')
This also works.
The Problem
In its original context, however, it does not work. I've confirmed that ${data} gets set just fine. And that ${1} contains the correct filename. What fails is the second line of the function. I've confirmed printf is being run (see, "Additional Info - Without The Redirect" below)... but the file its output is being redirected to is never created.
And I've been over the code a dozen-dozen times (not an exaggeration) and have yet to identify the cause. So, in desperation, I'm going to post it here and hope some kind soul will wade through my code and maybe spot the problem that I'm missing. I'd also happily take advice on improvements/replacements to my logging utility (in the hopes of tracking down the problem) or further troubleshooting steps.
Here is the original context. The important lines are 106-110, 136-140, 144-147, and 151-155
Additional Info
☛ PATH/Environment
The PATH is PATH=/usr/local/sbin:/usr/local/bin:/usr/bin. I believe this is being inherited from systemd (systemd=>dhcpcd.service=>dhcpcd=>dhcpcd-run-hooks=>dhcpcd.exit-hook).
dhcpcd-run-hooks (see "Complications" below) does clear the environment (keeping the above PATH) when it runs. Thus, I've added an example of the environment the script runs in to the "original context" gist. In this case, the environment when $reason == 'BOUND'. This is output by printenv | sort at the end of execution (and thus should show the final state of the environment).
NOTE: Be aware this is Arch Linux and the absence of /bin, /sbin, and /usr/sbin in the PATH is normal (they are just symlinks to /usr/bin anyway).
☛ Return Code
Inserting echo $? after the second line of the function gives me a return code of "0". This is true both with the redirect in line 2 and without (just the printf).
☛ Without The Redirect
Without the redirect, in the original context, the second line of the function prints the contents of ${data} to stdout (which is then captured by bashlog()) exactly as expected.
⚠️ Execute Instead of Source.
Turns out that $0 was /usr/lib/dhcpcd/dhcpcd-run-hooks rather than my script. Apparently dhcpcd-run-hooks doesn't execute the script... it sources it. I made some changes to line 196 to fix this.
♔ Aaaaaand that seems to have fixed all problems. ♔
I'm trying to confirm that was the silver bullet now... I didn't notice it was working till I had made several other changes as well. If I can confirm it I'll submit an answer.
Complications
What complicates matters quite a bit is that it's original context is a /etc/dhcpcd.exit-hook script. dhcpcd-run-hooks appears to eat all stderr and stdout which makes troubleshooting... unpleasant. I've implemented my own logging utility to capture the output of commands in the script and pass it to journald but it's not helping in this case. Either no error is being generated or, somehow, the error is not getting captured by my logging utility. The script is running as root and there is no mandatory access control installed so it shouldn't be a permissions issue.
I have a Perl CGI script that isn't working and I don't know how to start narrowing down the problem. What can I do?
Note: I'm adding the question because I really want to add my very lengthy answer to Stack Overflow. I keep externally linking to it in other answers and it deserves to be here. Don't be shy about editing my answer if you have something to add.
This answer is intended as a general framework for working through
problems with Perl CGI scripts and originally appeared on Perlmonks as Troubleshooting Perl CGI Scripts. It is not a complete guide to every
problem that you may encounter, nor a tutorial on bug squashing. It
is just the culmination of my experience debugging CGI scripts for twenty (plus!) years. This page seems to have had many different homes, and I seem
to forget it exists, so I'm adding it to the StackOverflow. You
can send any comments or suggestions to me at
bdfoy#cpan.org. It's also community wiki, but don't go too nuts. :)
Are you using Perl's built in features to help you find problems?
Turn on warnings to let Perl warn you about questionable parts of your code. You can do this from the command line with the -w switch so you don't have to change any code or add a pragma to every file:
% perl -w program.pl
However, you should force yourself to always clear up questionable code by adding the warnings pragma to all of your files:
use warnings;
If you need more information than the short warning message, use the diagnostics pragma to get more information, or look in the perldiag documentation:
use diagnostics;
Did you output a valid CGI header first?
The server is expecting the first output from a CGI script to be the CGI header. Typically that might be as simple as print "Content-type: text/plain\n\n"; or with CGI.pm and its derivatives, print header(). Some servers are sensitive to error output (on STDERR) showing up before standard output (on STDOUT).
Try sending errors to the browser
Add this line
use CGI::Carp 'fatalsToBrowser';
to your script. This also sends compilation errors to the browser window. Be sure to remove this before moving to a production environment, as the extra information can be a security risk.
What did the error log say?
Servers keep error logs (or they should, at least).
Error output from the server and from your script should
show up there. Find the error log and see what it says.
There isn't a standard place for log files. Look in the
server configuration for their location, or ask the server
admin. You can also use tools such as CGI::Carp
to keep your own log files.
What are the script's permissions?
If you see errors like "Permission denied" or "Method not
implemented", it probably means that your script is not
readable and executable by the web server user. On flavors
of Unix, changing the mode to 755 is recommended:
chmod 755 filename. Never set a mode to 777!
Are you using use strict?
Remember that Perl automatically creates variables when
you first use them. This is a feature, but sometimes can
cause bugs if you mistype a variable name. The pragma
use strict will help you find those sorts of
errors. It's annoying until you get used to it, but your
programming will improve significantly after awhile and
you will be free to make different mistakes.
Does the script compile?
You can check for compilation errors by using the -c
switch. Concentrate on the first errors reported. Rinse,
repeat. If you are getting really strange errors, check to
ensure that your script has the right line endings. If you
FTP in binary mode, checkout from CVS, or something else that
does not handle line end translation, the web server may see
your script as one big line. Transfer Perl scripts in ASCII
mode.
Is the script complaining about insecure dependencies?
If your script complains about insecure dependencies, you
are probably using the -T switch to turn on taint mode, which is
a good thing since it keeps you have passing unchecked data to the shell. If
it is complaining it is doing its job to help us write more secure scripts. Any
data originating from outside of the program (i.e. the environment)
is considered tainted. Environment variables such as PATH and
LD_LIBRARY_PATH
are particularly troublesome. You have to set these to a safe value
or unset them completely, as I recommend. You should be using absolute
paths anyway. If taint checking complains about something else,
make sure that you have untainted the data. See perlsec
man page for details.
What happens when you run it from the command line?
Does the script output what you expect when run from the
command line? Is the header output first, followed by a
blank line? Remember that STDERR may be merged with STDOUT
if you are on a terminal (e.g. an interactive session), and
due to buffering may show up in a jumbled order. Turn on
Perl's autoflush feature by setting $| to a
true value. Typically you might see $|++; in
CGI programs. Once set, every print and write will
immediately go to the output rather than being buffered.
You have to set this for each filehandle. Use select to
change the default filehandle, like so:
$|++; #sets $| for STDOUT
$old_handle = select( STDERR ); #change to STDERR
$|++; #sets $| for STDERR
select( $old_handle ); #change back to STDOUT
Either way, the first thing output should be the CGI header
followed by a blank line.
What happens when you run it from the command line with a CGI-like environment?
The web server environment is usually a lot more limited
than your command line environment, and has extra
information about the request. If your script runs fine
from the command line, you might try simulating a web server
environment. If the problem appears, you have an
environment problem.
Unset or remove these variables
PATH
LD_LIBRARY_PATH
all ORACLE_* variables
Set these variables
REQUEST_METHOD (set to GET, HEAD, or POST as appropriate)
SERVER_PORT (set to 80, usually)
REMOTE_USER (if you are doing protected access stuff)
Recent versions of CGI.pm ( > 2.75 ) require the -debug flag to
get the old (useful) behavior, so you might have to add it to
your CGI.pm imports.
use CGI qw(-debug)
Are you using die() or warn?
Those functions print to STDERR unless you have redefined
them. They don't output a CGI header, either. You can get
the same functionality with packages such as CGI::Carp
What happens after you clear the browser cache?
If you think your script is doing the right thing, and
when you perform the request manually you get the right
output, the browser might be the culprit. Clear the cache
and set the cache size to zero while testing. Remember that
some browsers are really stupid and won't actually reload
new content even though you tell it to do so. This is
especially prevalent in cases where the URL path is the
same, but the content changes (e.g. dynamic images).
Is the script where you think it is?
The file system path to a script is not necessarily
directly related to the URL path to the script. Make sure
you have the right directory, even if you have to write a
short test script to test this. Furthermore, are you sure
that you are modifying the correct file? If you don't see
any effect with your changes, you might be modifying a
different file, or uploading a file to the wrong place.
(This is, by the way, my most frequent cause of such trouble
;)
Are you using CGI.pm, or a derivative of it?
If your problem is related to parsing the CGI input and you
aren't using a widely tested module like CGI.pm, CGI::Request,
CGI::Simple or CGI::Lite, use the module and get on with life.
CGI.pm has a cgi-lib.pl compatibility mode which can help you solve input
problems due to older CGI parser implementations.
Did you use absolute paths?
If you are running external commands with
system, back ticks, or other IPC facilities,
you should use an absolute path to the external program.
Not only do you know exactly what you are running, but you
avoid some security problems as well. If you are opening
files for either reading or writing, use an absolute path.
The CGI script may have a different idea about the current
directory than you do. Alternatively, you can do an
explicit chdir() to put you in the right place.
Did you check your return values?
Most Perl functions will tell you if they worked or not
and will set $! on failure. Did you check the
return value and examine $! for error messages? Did you check
$# if you were using eval?
Which version of Perl are you using?
The latest stable version of Perl is 5.28 (or not, depending on when this was last edited). Are you using an older version? Different versions of Perl may have different ideas of warnings.
Which web server are you using?
Different servers may act differently in the same
situation. The same server product may act differently with
different configurations. Include as much of this
information as you can in any request for help.
Did you check the server documentation?
Serious CGI programmers should know as much about the
server as possible - including not only the server features
and behavior, but also the local configuration. The
documentation for your server might not be available to you
if you are using a commercial product. Otherwise, the
documentation should be on your server. If it isn't, look
for it on the web.
Did you search the archives of comp.infosystems.www.authoring.cgi?
This use to be useful but all the good posters have either died or wandered off.
It's likely that someone has had your problem before,
and that someone (possibly me) has answered it in this
newsgroup. Although this newsgroup has passed its heyday, the collected wisdom from the past can sometimes be useful.
Can you reproduce the problem with a short test script?
In large systems, it may be difficult to track down a bug
since so many things are happening. Try to reproduce the problem
behavior with the shortest possible script. Knowing the problem
is most of the fix. This may be certainly time-consuming, but you
haven't found the problem yet and you're running out of options. :)
Did you decide to go see a movie?
Seriously. Sometimes we can get so wrapped up in the problem that we
develop "perceptual narrowing" (tunnel vision). Taking a break,
getting a cup of coffee, or blasting some bad guys in [Duke Nukem,Quake,Doom,Halo,COD] might give you
the fresh perspective that you need to re-approach the problem.
Have you vocalized the problem?
Seriously again. Sometimes explaining the problem aloud
leads us to our own answers. Talk to the penguin (plush toy) because
your co-workers aren't listening. If you are interested in this
as a serious debugging tool (and I do recommend it if you haven't
found the problem by now), you might also like to read The Psychology
of Computer Programming.
I think CGI::Debug is worth mentioning as well.
Are you using an error handler while you are debugging?
die statements and other fatal run-time and compile-time errors get
printed to STDERR, which can be hard to find and may be conflated with
messages from other web pages at your site. While you're debugging your
script, it's a good idea to get the fatal error messages to display in your
browser somehow.
One way to do this is to call
use CGI::Carp qw(fatalsToBrowser);
at the top of your script. That call will install a $SIG{__DIE__} handler (see perlvar)display fatal errors in your browser, prepending it with a valid header if necessary. Another CGI debugging trick that I used before I ever heard of CGI::Carp was to
use eval with the DATA and __END__ facilities on the script to catch compile-time errors:
#!/usr/bin/perl
eval join'', <DATA>;
if ($#) { print "Content-type: text/plain:\n\nError in the script:\n$#\n; }
__DATA__
# ... actual CGI script starts here
This more verbose technique has a slight advantage over CGI::Carp in that it will catch more compile-time errors.
Update: I've never used it, but it looks like CGI::Debug, as Mikael S
suggested, is also a very useful and configurable tool for this purpose.
I wonder how come no-one mentioned the PERLDB_OPTS option called RemotePort; although admittedly, there aren't many working examples on the web (RemotePort isn't even mentioned in perldebug) - and it was kinda problematic for me to come up with this one, but here it goes (it being a Linux example).
To do a proper example, first I needed something that can do a very simple simulation of a CGI web server, preferably through a single command line. After finding Simple command line web server for running cgis. (perlmonks.org), I found the IO::All - A Tiny Web Server to be applicable for this test.
Here, I'll work in the /tmp directory; the CGI script will be /tmp/test.pl (included below). Note that the IO::All server will only serve executable files in the same directory as CGI, so chmod +x test.pl is required here. So, to do the usual CGI test run, I change directory to /tmp in the terminal, and run the one-liner web server there:
$ cd /tmp
$ perl -MIO::All -e 'io(":8080")->fork->accept->(sub { $_[0] < io(-x $1 ? "./$1 |" : $1) if /^GET \/(.*) / })'
The webserver command will block in the terminal, and will otherwise start the web server locally (on 127.0.0.1 or localhost) - afterwards, I can go to a web browser, and request this address:
http://127.0.0.1:8080/test.pl
... and I should observe the prints made by test.pl being loaded - and shown - in the web browser.
Now, to debug this script with RemotePort, first we need a listener on the network, through which we will interact with the Perl debugger; we can use the command line tool netcat (nc, saw that here: Perl如何remote debug?). So, first run the netcat listener in one terminal - where it will block and wait for connections on port 7234 (which will be our debug port):
$ nc -l 7234
Then, we'd want perl to start in debug mode with RemotePort, when the test.pl has been called (even in CGI mode, through the server). This, in Linux, can be done using the following "shebang wrapper" script - which here also needs to be in /tmp, and must be made executable:
cd /tmp
cat > perldbgcall.sh <<'EOF'
#!/bin/bash
PERLDB_OPTS="RemotePort=localhost:7234" perl -d -e "do '$#'"
EOF
chmod +x perldbgcall.sh
This is kind of a tricky thing - see shell script - How can I use environment variables in my shebang? - Unix & Linux Stack Exchange. But, the trick here seems to be not to fork the perl interpreter which handles test.pl - so once we hit it, we don't exec, but instead we call perl "plainly", and basically "source" our test.pl script using do (see How do I run a Perl script from within a Perl script?).
Now that we have perldbgcall.sh in /tmp - we can change the test.pl file, so that it refers to this executable file on its shebang line (instead of the usual Perl interpreter) - here is /tmp/test.pl modified thus:
#!./perldbgcall.sh
# this is test.pl
use 5.10.1;
use warnings;
use strict;
my $b = '1';
my $a = sub { "hello $b there" };
$b = '2';
print "YEAH " . $a->() . " CMON\n";
$b = '3';
print "CMON " . &$a . " YEAH\n";
$DB::single=1; # BREAKPOINT
$b = '4';
print "STEP " . &$a . " NOW\n";
$b = '5';
print "STEP " . &$a . " AGAIN\n";
Now, both test.pl and its new shebang handler, perldbgcall.sh, are in /tmp; and we have nc listening for debug connections on port 7234 - so we can finally open another terminal window, change directory to /tmp, and run the one-liner webserver (which will listen for web connections on port 8080) there:
cd /tmp
perl -MIO::All -e 'io(":8080")->fork->accept->(sub { $_[0] < io(-x $1 ? "./$1 |" : $1) if /^GET \/(.*) / })'
After this is done, we can go to our web browser, and request the same address, http://127.0.0.1:8080/test.pl. However, now when the webserver tries to execute the script, it will do so through perldbgcall.sh shebang - which will start perl in remote debugger mode. Thus, the script execution will pause - and so the web browser will lock, waiting for data. We can now switch to the netcat terminal, and we should see the familiar Perl debugger text - however, output through nc:
$ nc -l 7234
Loading DB routines from perl5db.pl version 1.32
Editor support available.
Enter h or `h h' for help, or `man perldebug' for more help.
main::(-e:1): do './test.pl'
DB<1> r
main::(./test.pl:29): $b = '4';
DB<1>
As the snippet shows, we now basically use nc as a "terminal" - so we can type r (and Enter) for "run" - and the script will run up do the breakpoint statement (see also In perl, what is the difference between $DB::single = 1 and 2?), before stopping again (note at that point, the browser will still lock).
So, now we can, say, step through the rest of test.pl, through the nc terminal:
....
main::(./test.pl:29): $b = '4';
DB<1> n
main::(./test.pl:30): print "STEP " . &$a . " NOW\n";
DB<1> n
main::(./test.pl:31): $b = '5';
DB<1> n
main::(./test.pl:32): print "STEP " . &$a . " AGAIN\n";
DB<1> n
Debugged program terminated. Use q to quit or R to restart,
use o inhibit_exit to avoid stopping after program termination,
h q, h R or h o to get additional info.
DB<1>
... however, also at this point, the browser locks and waits for data. Only after we exit the debugger with q:
DB<1> q
$
... does the browser stop locking - and finally displays the (complete) output of test.pl:
YEAH hello 2 there CMON
CMON hello 3 there YEAH
STEP hello 4 there NOW
STEP hello 5 there AGAIN
Of course, this kind of debug can be done even without running the web server - however, the neat thing here, is that we don't touch the web server at all; we trigger execution "natively" (for CGI) from a web browser - and the only change needed in the CGI script itself, is the change of shebang (and of course, the presence of the shebang wrapper script, as executable file in the same directory).
Well, hope this helps someone - I sure would have loved to have stumbled upon this, instead of writing it myself :)
Cheers!
For me, I use log4perl . It's quite useful and easy.
use Log::Log4perl qw(:easy);
Log::Log4perl->easy_init( { level => $DEBUG, file => ">>d:\\tokyo.log" } );
my $logger = Log::Log4perl::get_logger();
$logger->debug("your log message");
Honestly you can do all the fun stuff above this post.
ALTHOUGH, the simplest and most proactive solution I found was to just "print it".
In example:
(Normal code)
`$somecommand`;
To see if it's doing what I really want it to do:
(Trouble shooting)
print "$somecommand";
It will probably also be worth mentioning that Perl will always tell you on what line the error occurs when you execute the Perl script from the command line. (An SSH Session for example)
I will usually do this if all else fails. I will SSH into the server and manually execute the Perl script. For example:
% perl myscript.cgi
If there is a problem then Perl will tell you about it. This debugging method does away with any file permission related issues or web browser or web server issues.
You may run the perl cgi-script in terminal using the below command
$ perl filename.cgi
It interpret the code and provide result with HTML code.
It will report the error if any.
A trivial situation - the script has finished it's execution, and all the variables used on it's way remained.
I'm looking for a way the script could unset all used by it variables ONLY, as there are many other scripts setting their stuff...
'exec bash' is not an option.
EG from my imagination:
function setVariables {
A="~/"
B=$(du -sh /smth)
C="tralala"
}
setVariables
function cleanup {
readarray -t args < <(setVariables)
set -u "${args[#]}"
}
cleanup
How to achieve this?
Like already suggested in comments, the trivial solution is to put the commands in a script instead of in a function. The script runs in a subprocess with its own environment, and doesn't change anything in the parent. When the child finishes, nothing from its environment is left.
If you need to use a function, Bash has a local keyword which makes the variable's scope local to the current function. When the function ends, all variables are reset to their state from before the function ran (unset if they were unset, previous value if they were set).
If you want to set variables and have them set outside of a function, but have a simple way to revert them to their original value, you really have to build that yourself. Look at how Python's virtualenv does it, for example (a common and popular example, though not necessarily the absolutely most robust) -- it basically writes out the previous values to the definition of the deactivate command which disables the virtual environment and (attempts to) return things to the way they were before you ran activate.
# bash 4+ only!
setVariables () {
declare -A _setvariables_old=([A]="$A" [B]="$B" [C]="$C")
A="~/"
B=$(du -sh /smth)
C="tralala"
}
setVariables
:
cleanup () {
local var
for var in "${!_setvariables_old[#]}"; do
printf -v "$var" "%s" "${_setvariables_old[$var]}"
done
unset _setvariables_old
}
This leaks slightly (what if _setvariables_old is a variable you want to preserve!?) and doesn't know how to unset things; it just reverts to an empty string if something was unset before you started.
Summary
I am trying to understand a complicated chain of Makefiles, in order to get a build to succeed. I narrowed down my problem to this bit in our build script:
INF_RL=`make -f $BUILD_ROOT/Makefile BUILD_ROOT_MAKEFILE= show__BUILD_INF_RL`
$INF_RL/$BUILD_UTILS_RELDIR/BuildAll.sh
$INF_RL is being set to an empty string (or not being set). If I replace the first line with
INF_RL=/foo_rel_linx86/infrastructure_release/v8.0.14
in order to hardcode what I know $INF_RL is supposed to be, then the build goes smoothly. But I want to know how to fix this the proper way.
What I've Tried / Thought
My first thought was that make -f is failing. So I tried it in my shell:
% make -f $BUILD_ROOT/Makefile BUILD_ROOT_MAKEFILE= show__BUILD_INF_RL
% setenv | grep BUILD_ROOT
BUILD_ROOT=/userhome/andrew.cheong/TPS
Indeed, it returned an empty string. But what conclusion could I draw from this? I wasn't sure if the shell was the same thing as the environment / scope in which Make was chaining together its Makefiles. I abandoned this investigation.
Next, I looked into show__BUILD_INF_RL, which seemed to be defined in $BUILD_ROOT/Makefile:
BUILD_ROOT_MAKEFILE = 1
MAKE_DIRS = src
CASE_KITS = tpsIn tpsOut
REQUIRED_VERSIONS = "case.v$(INF_VS)"
all:
## These next 3 rules allows any variable set in this makefile (and therefore
## the included makefile.include to have it's value echoed from the command
## "make show_<variableName>"
## NOTE: the "disp" target is vital as it allows the show_% implicit rule to be
## recognised as such - implicit rules *must* have a target.
show_% := DISPLAY_MACRO = $(#:show_%=%)
show_% : disp
# echo $($(DISPLAY_MACRO))
disp:
include $(BUILD_ROOT)/makefile.include
Here, I faced more questions:
What is BUILD_ROOT_MAKEFILE for? Why is it set to 1, then seemingly something else in the make -f command?
In the make -f command, is BUILD_ROOT_MAKEFILE= its own argument? If so, what kind of target or rule is that? Otherwise, why is it being set to the macro?
In $BUILD_ROOT, there is another file, makefile.LINUX_X86.include:
BUILD_INF_RL = /foo_rel_linx86/infrastructure_release/v$(INF_VS)
$(warning $(BUILD_INF_RL))
BUILD_UTILS = $(BUILD_INF_RL)/build-utils_LINUX_X86
Though a completely ignorant guess, I think BUILD_INF_RL is being set here, and intended to be extracted into the build script's variable INF_RL when the macro show__BUILD_INF_RL is invoked. I added the middle line to see if it was indeed being set, and indeed, I get this output when running the build script:
/userhome/andrew.cheong/TPS/makefile.LINUX_X86.include:3: /foo_rel_linx86/infrastructure_release/v8.0.14
i.e. Looks like what I've hardcoded way above! But why doesn't it make it into INF_RL? There is yet another file, makefile.include, also in $BUILD_ROOT:
#
# INCLUDE THIS FILE AS THE LAST LINE IN THE LOCAL MAKEFILE
#
# makefile.include - use this file to define global build settings
# e.g. infrastructure version and location, or third-party
#
# supported macros in addition to build-utils-makefile.include
#
# BUILD_INF_RL : optional, specification of infrastructure release location
# defaults to vdev_build area
#
include $(BUILD_ROOT)/../../makefile.include.$(BUILD_ARCH).Versions
#include $(BUILD_UTILS)/makefile.archdef.include
include $(BUILD_ROOT)/makefile.$(BUILD_ARCH).include
$(warning $(BUILD_INF_RL))
_BUILD_INF_RL = $(BUILD_INF_RL)
# place the results at the root of the infdemo tree
BUILD_DEST = $(BUILD_ROOT)
INCLUDE_DIRS += $(BUILD_INF_RL)/core/$(BUILD_TARGET)/include
LINK_DIRS += $(BUILD_INF_RL)/core/$(BUILD_TARGET)/lib
# libraries required for a typical fidessa app, including OA and DB access
FIDEVMAPP_LIBS = FidApp FidInf FidCore Fidevm
include $(BUILD_UTILS)/makefile.include
That $(warning ...) is again mine, and when running the build script, I get:
/userhome/andrew.cheong/TPS/makefile.include:18: /foo_rel_linx86/infrastructure_release/v8.0.14
The Question
The fact that both $(warning ...)s show up when I run the build script that's calling the make -f ... show__BUILD_INF_RL, tells me that those Makefiles are being included. Then what is causing the macro to fail and return an empty string instead of the correct INF_RL path?
Historical Notes
These build scripts were written at a time when we were only compiling for Solaris. (The scripts were based on templates written by an infrastructure team that loosely accounted for both Solaris and Linux, but we never ran the Linux branch, as it was unnecessary.) We are now fully migrating to Linux, and hitting this issue. The reason I'm skeptical of it being a Linux versus Solaris issue is that we have at least four other products that use a similar Makefile chain and have been migrated with no issues. Not sure why this one in particular is behaving different.
Your question got very long and complex so I didn't read it all... for SO it's often better if you just ask a specific targeted question that you want to know the answer to, with a simple repro case.
I can't say why different makefiles behave differently, but this line:
show_% := DISPLAY_MACRO = $(#:show_%=%)
seems really wrong to me. This is (a) setting the variable show_%, which don't actually use anywhere, (b) to the simply expanded string DISPLAY_MACRO = because at this point in the makefile the variable $# is not set to any value.
Maybe you wanted this line to be this instead:
show_% : DISPLAY_MACRO = $(#:show_%=%)
(note : not :=) so that it's a pattern-specific variable assignment, not a simple variable assignment?
I have a environment variable set with name $MY_ENV_VARIABLE.
How do I use this variable inside my makefile to (for example) include some source files?
LOCAL_SRC_FILES = $(MY_ENV_VARIABLE)/libDEMO.so
Something like above doesn't seem to work.
Note: in my case this is needed for building with the Android NDK but I guess this applies to make in general.
Just to add some information...
The syntax to access the environment variable in make is like other variables in make...
#export the variable. e.g. in the terminal,
export MY_ENV_VARIABLE="hello world"
...
#in the makefile (replace before call)
echo $(MY_ENV_VARIABLE)
This performs the substitution before executing the commmand. If you instead, want the substitution to happen during the command execution, you need to escape the $ (For example, echo $MY_ENV_VARIABLE is incorrect and will attempt to substitute the variable M in make, and append it to Y_ENV_VARIABLE)...
#in the makefile (replace during call)
echo $$MY_ENV_VARIABLE
Make sure you exported the variable from your shell. Running:
echo $MY_ENV_VARIABLE
shows you whether it's set in your shell. But to know whether you've exported it so that subshells and other sub-commands (like make) can see it try running:
env | grep MY_ENV_VARIABLE
If it's not there, be sure to run export MY_ENV_VARIABLE before running make.
That's all you need to do: make automatically imports all environment variables as make variables when it starts up.
I just had a similar issue (under Cygwin):
Running echo $OSTYPE on the shell prints the value, but
running env | grep OSTYPE doesn't give any output.
As I can't guarantee that this variable is exported on all machines I want to run that makefile on, I used the following to get the variable from within the makefile:
OSTYPE = $(shell echo $$OSTYPE)
Which of course can also be used within a condition like the following:
ifeq ($(shell echo $$OSTYPE),cygwin)
# ...do something...
else
# ...do something else...
endif
EDIT:
Some things I found after experimenting with the info from jozxyqk's answer, all from within the makefile:
If I run #echo $$OSTYPE or #echo "$$OSTYPE" in a recipe, the variable is successfully expanded into cygwin.
However, using that in a condition like ifeq ($$OSTYPE,cygwin) or ifeq ("$$OSTYPE","cygwin") doesn't expand it.
Thus it is logical that first setting a variable like TEST = "$$OSTYPE" will lead to echo $(TEST) printing cygwin (the expansion is done by the echo call) but that doesn't work in a condition - ifeq ($(TEST),cygwin) is false.