I'm trying to do this in my Makefile:
VAL=
TARGET1:
VAL= ... #compute value of VAL
#run some command that uses the value of VAL
TARGET2:
$(MAKE) TARGET1
#run other command that uses the value of VAL
But it turns out that value of VAL is reset when TARGET! completes in TARGET2. Thus the computed value of VAL is not available when I try to run the other command in TARGET2. Is there any way to keep the value computed in TARGET1? Thanks.
You have a fundamental misconception. The variable VAL that is set in the TARGET1 recipe is not a make variable at all: it's a shell variable. You can tell because if you change the syntax of the assignment to be something else that is still a valid make variable assignment but is not a valid shell variable assignment, like:
TARGET1:
VAL := foo
it will give you a syntax error. Basically in make, any recipe line (lines after a target that begin with a TAB character) are not interpreted by make at all: they're passed to a shell that make invokes. Nothing that happens in that shell can have any effect on the value of make variables, etc. of course.
You don't give us much detail. You don't say whether the command uses the variable from the environment or via the command line. You don't say what version of make you're using. If it's GNU make, you have a number of options. The simplest one is to set the value always; if it requires shell syntax you can use the shell function:
VAL := $(shell #compute value of VAL)
TARGET1:
#run some command that uses $(VAL)
TARGET2:
#run another command that uses $(vAL)
Before we give you more possibilities we need to understand the requirements: if you HAVE to have the value set in TARGET1 we need to know why, before we can offer possible solutions.
Related
-- Edit : Resolved. See answer.
Background:
I'm writing a shell that will perform some extra actions required on our system when someone resizes a database.
The shell is written in ksh (requirement), the OS is Solaris 5.10 .
The problem is with one of the checks, which verifies there's enough free space on the underlying OS.
Problem:
The check reads the df -k line for root, which is what I check in this step, and prints it to a file. I then "read" the contents into variables which I use in calculations.
Unfortunately, when I try to run an arithmetic operation on one of the variables, I get an error indicating it is null. And a debug output line I've placed after that line verifies that it is null... It lost it's value...
I've tried every method of doing this I could find online, they work when I run it manually, but not inside the shell file.
(* The file does have #!/usr/bin/ksh)
Code:
df -k | grep "rpool/ROOT" > dftest.out
RPOOL_NAME=""; declare -i TOTAL_SIZE=0; USED_SPACE=0; AVAILABLE_SPACE=0; AVAILABLE_PERCENT=0; RSIGN=""
read RPOOL_NAME TOTAL_SIZE USED_SPACE AVAILABLE_SPACE AVAILABLE_PERCENT RSIGN < dftest.out
\rm dftest.out
echo $RPOOL_NAME $TOTAL_SIZE $USED_SPACE $AVAILABLE_SPACE $AVAILABLE_PERCENT $RSIGN
((TOTAL_SIZE=$TOTAL_SIZE/1024))
This is the result:
DBResize.sh[11]: TOTAL_SIZE=/1024: syntax error
I'm pulling hairs at this point, any help would be appreciated.
The code you posted cannot produce the output you posted. Most obviously, the error is signalled at line 11 but you posted fewer than 11 lines of code. The previous lines may matter. Always post complete code when you ask for help.
More concretely, the declare command doesn't exist in ksh, it's a bash thing. You can achieve the same result with typeset (declare is a bash equivalent to typeset, but not all options are the same). Either you're executing this script with bash, or there's another error message about declare, or you've defined some additional commands including declare which may change the behavior of this code.
None of this should have an impact on the particular problem that you're posting about, however. The variables created by read remain assigned until the end of the subshell, i.e. until the code hits a ), the end of a pipe (left-hand side of the pipe only in ksh), etc.
About the use of declare or typeset, note that you're only declaring TOTAL_SIZE as an integer. For the other variables, you're just assigning a value which happens to consist exclusively of digits. It doesn't matter for the code you posted, but it's probably not what you meant.
One thing that may be happening is that grep matches nothing, and therefore read reads an empty line. You should check for errors. Use set -e in scripts to exit at the first error. (There are cases where set -e doesn't catch errors, but it's a good start.)
Another thing that may be happening is that df is splitting its output onto multiple lines because the first column containing the filesystem name is too large. To prevent this splitting, pass the option -P.
Using a temporary file is fragile: the code may be executed in a read-only directory, another process may want to access the same file at the same time... Here a temporary file is useless. Just pipe directly into read. In ksh (unlike most other sh variants including bash), the right-hand side of a pipe runs in the main shell, so assignments to variables in the right-hand side of a pipe remain available in the following commands.
It doesn't matter in this particular script, but you can use a variable without $ in an arithmetic expression. Using $ substitutes a string which can have confusing results, e.g. a='1+2'; $((a*3)) expands to 7. Not using $ uses the numerical value (in ksh, a='1+2'; $((a*3)) expands to 9; in some sh implementations you get an error because a's value is not numeric).
#!/usr/bin/ksh
set -e
typeset -i TOTAL_SIZE=0 USED_SPACE=0 AVAILABLE_SPACE=0 AVAILABLE_PERCENT=0
df -Pk | grep "rpool/ROOT" | read RPOOL_NAME TOTAL_SIZE USED_SPACE AVAILABLE_SPACE AVAILABLE_PERCENT RSIGN
echo $RPOOL_NAME $TOTAL_SIZE $USED_SPACE $AVAILABLE_SPACE $AVAILABLE_PERCENT $RSIGN
((TOTAL_SIZE=TOTAL_SIZE/1024))
Strange...when I get rid of your "declare" line, your original code seems to work perfectly well (at least with ksh on Linux)
The code :
#!/bin/ksh
df -k | grep "/home" > dftest.out
read RPOOL_NAME TOTAL_SIZE USED_SPACE AVAILABLE_SPACE AVAILABLE_PERCENT RSIGN < dftest.out
\rm dftest.out
echo $RPOOL_NAME $TOTAL_SIZE $USED_SPACE $AVAILABLE_SPACE $AVAILABLE_PERCENT $RSIGN
((TOTAL_SIZE=$TOTAL_SIZE/1024))
print $TOTAL_SIZE
The result :
32962416 5732492 25552588 19% /home
5598
Which are the value a simple df -k is returning. The variables seem to last.
For those interested, I have figured out that it is not possible to use "read" the way I was using it.
The variable values assigned by "read" simply "do not last".
To remedy this, I have applied the less than ideal solution of using the standard "while read" format, and inside the loop, echo selected variables into a variable file.
Once said file was created, I just "loaded" it.
(pseudo code:)
LOOP START
echo "VAR_A="$VAR_A"; VAR_B="$VAR_B";" > somefile.out
LOOP END
. somefile.out
I try to convert a filename such as foo/bar/baz.proto into something like foo/bar/Baz.java in my Makefile. For this purpose, I thought I could use sed. However, it seems that the command does not work as expected:
uppercase_file = $(shell echo "$(1)" | sed 's/\(.*\/\)\(.*\)/\1\u\2/')
# generated Java sources
PROTO_JAVA_TARGETS := ${PROTO_SPECS:$(SRCDIR)/%.proto=$(JAVAGEN)/$(call uppercase_file,%).java}
When I try to run the sed command on the command line it seems to work:
~$ echo "foo/bar/baz" | sed 's/\(.*\/\)\(.*\)/\1\u\2/'
foo/bar/Baz
Any ideas why this does not work inside the Makefile?
UPDATE:
The java files are generated with the following target:
$(JAVAGEN)/%.java: $(SRCDIR)/%.proto
How can I apply the substitution also for targets?
GNU Make does not replace % character in the replacement part of a substitution reference (which is basically a syntactic sugar for patsubst) if it is part of a variable reference. I have not found this behavior described in the documentation, but you can look it implemented in the source code (the relevant function I believe is find_char_unquote).
I suggest moving the call out of the substitution reference, since uppercase_file obviously works properly on any file path:
PROTO_JAVA_TARGETS := $(call uppercase_file,${PROTO_SPECS:$(SRCDIR)/%.proto=$(JAVAGEN)/%.java})
If $(PROTO_SPECS) resolves not to a single element, but rather to a list of elements, you can use foreach to call the function on every elements of a processed list:
PROTO_JAVA_TARGETS := $(foreach JAVA,${PROTO_SPECS:$(SRCDIR)/%.proto=$(JAVAGEN)/%.java},$(call uppercase_file,$(JAVA)))
The java files are generated with the following target: $(JAVAGEN)/%.java: $(SRCDIR)/%.proto
How can I apply the substitution also for targets?
Since Make matches targets first, and there is no way to run sed backwards, what you need here is either define an inverse function, or generate multiple explicit rules. I will show the latter approach.
define java_from_proto
$(call uppercase_file,$(1:$(SRCDIR)/%.proto=$(JAVAGEN)/%.java)): $1
# Whatever recipe you use.
# Use `$$#`, `$$<` and so on instead of `$#` or `$<`.
endef
$(foreach PROTO,$(PROTO_SPECS),$(eval $(call java_from_proto,$(PROTO))))
We basically generate one rule per file in $(PROTO_SPEC) using a multiline variable syntax, and then use eval to install that rule. There is also a very similar example on this documentation page that can be helpful.
I've been searching all over the place and since I'm taking my first steps in PERL this might be one of he dumbest questions but here it goes.
So I'm creating a script to manage my windows and later bind it to keyboard shortcuts, so I I'm trying to run a command and passing some variables:
my $command = `wmctrl -r :ACTIVE: -e 0,0,0,$monitors->{1}->{'width'}/2,$monitors->{1}->{'height'}`;
But I get an error saying I'm not passing the right parameters to the command, but if I do this, everything works great:
my $test = $monitors->{1}->{'width'}/2;
my $command = `wmctrl -r :ACTIVE: -e 0,0,0,$test,$monitors->{1}->{'height'}`;
So do I really have to do this? assign it first to a variable and then pass it, or there's a more elegant way of doing it?
The backticks operator (or the qx{}) accepts A string which is (possibly) interpolated. So accepts string and not expression like $var/2.
Thats mean than the $variables ($var->{1}->{some} too) are expanded but not the arithmetic expressions.
Therefore your 2 step variant works, but not the first.
If you want evaluate an expression inside the string you can use the next:
my $ans=42;
print "The #{[ $ans/2 ]} is only the half of answer\n";
prints
The 21 is only the half of answer
but it is not very readable, so better and elegant is what you're already doing - calculate the command argument in andvace, and to the qx{} or backticks only pass the calculated $variables.
Can any one explain this format?
${name:-$devi}
Example:
"${1+"$#"}" will check for that first variable to be set , if not it will use that
command line argument.
What is the difference between :- and + between those variables?
${var:-val}
is the same as ${var} if var is set and non-null, otherwise it expands to val. This is used to specify a default value for a variable.
${var+val}
expands to nothing if var is unset, otherwise it expands to val. This is used to supply an alternate value for a variable.
"${1+"$#"}"
is a workaround for a bug in old shell versions. If you just wrote "$#", it would expand to "" when no arguments were supplied, instead of expanding to nothing; the script would then act as if a single, empty argument had been supplied. This syntax first checks whether $1 is set -- if there's no first argument, then there are obviously no arguments at all. If $1 is unset, it expands to nothing, otherwise it's safe to use "$#".
Most modern shell versions don't have this bug, so you can just write "$#" without the special check. I'm not sure if there are any other common use cases for the + construct in shell variable expansion.
Quick question... I'm trying the following:
set changedir "cd $JSDIR/"
eval $changedir
..Where $JSDIR is defined already. Running this script gives the error: "set: Variable name must begin with a letter."
What's the fix?
Thanks.
That's not an error message generated by Tcl, because Tcl's variables most definitely do not need to begin with a letter. OK, it tends to be convenient to keep them alphanumeric because the $var shorthand syntax is more restrictive than the general space of variable names, but the set var form can handle virtually anything.
I'm guessing that script is being evaluated by something that isn't Tcl, perhaps bash?
Try to set changedir cd ${JSDIR/} instead
This message can appear when in fact the variable name is entirely correct, and the real problem is that the variable value needs to be quoted. Try instead of: set changedir "cd $JSDIR//"