In a Makefile, I have a rule to make a figure list from a LaTeX paper by piping the
output from a script to a perl expression that increments figure numbers $f++ and prepends Figure $f: to the lines.
From a command line, it works fine, as follows:
% texdepend -format=1 -print=f MilestonesProject | perl -pe 'unless (/^#/){$f++; s/^/Figure $f: /}' > FIGLIST
generating FIGLIST:
# texdepend, v0.96 (Michael Friendly (friendly#yorku.ca))
# commandline: texdepend -format=1 -print=f MilestonesProject
# FIGS =
Figure 1: fig/langren-google-overlay2.pdf
Figure 2: fig/mileyears4.png
Figure 3: fig/datavis-schema-3.pdf
Figure 4: fig/datavis-timeline2.png
...
I can't figure out how to make this work in a Makefile, because the $f stuff in the perl expression gets interpreted by make and I can't figure out how to quote it or otherwise
make it invisible to make.
My most recent attempt in my Makefile:
## Generate FIGLIST; doesnt work due to Make quoting
FIGLIST:
$(TEXDEPEND) -format=1 -print=f $(MAIN) | perl -pe 'unless (/^#/){\$f++; s/^/Figure \$f: /}' > FIGLIST
Can someone help?
-Michael
Double the dollar signs.
## Generate FIGLIST
FIGLIST:
$(TEXDEPEND) -format=1 -print=f $(MAIN) \
| perl -pe 'unless (/^\#/){$$f++; s/^/Figure $$f: /}' > $#
You may need to backslash-escape the comment sign as well. I did so just in case.
See also http://www.gnu.org/software/make/manual/html_node/Variables-in-Recipes.html#Variables-in-Recipes
Related
The follwoing code is Perl script, grep lines with 'Stage' from hostlog. and then line by line match the content with regex, if find add the count by 1:
$command = 'grep \'Stage \' '. $hostlog;
#stage_info = qx($command);
foreach (#stage_info) {
if ( /Stage\s(\d+)\s(.*)/ ) {
$stage_number = $stage_number+1;
}
}
so how to do this in linux shell? Based on my test, the we can not loop line by line, since there is space inside.
That is a horrible piece of Perl code you've got there. Here's why:
It looks like you are not using use strict; use warnings;. That is a huge mistake, and will not prevent errors, it will just hide them.
Using qx() to grep lines from a file is a completely redundant thing to do, as this is what Perl does best itself. "Shelling out" a process like that most often slows your program down.
Use some whitespace to make your code readable. This is hard to read, and looks more complicated than it is.
You capture strings by using parentheses in your regex, but you never use these strings.
Re: $stage_number=$stage_number+1, see point 3. And also, this can be written $stage_number++. Using the ++ operator will make your code clearer, will prevent the uninitialized warnings, and save you some typing.
Here is what your code should look like:
use strict;
use warnings;
open my $fh, "<", $hostlog or die "Cannot open $hostlog for reading: $!";
while (<$fh>) {
if (/Stage\s\d+/) {
$stage_number++;
}
}
You're not doing anything with the internal captures, so why bother? You could do everything with a grep:
$ stage_number=$(grep -E 'Stage\s\d+\s' | wc -l)
This is using extended regular expressions. I believe the GNU version takes these without a -E parameter, and in Solaris, even the egrep command might not quite allow for this regular expression.
If there's something more you have to do, you've got to explain it in your question.
If I understand the issue correctly, you should be able to do this just fine in the shell:
while read; do
if echo ${REPLY} | grep -q -P "'Stage' "; then
# Do what you need to do
fi
done < test.log
Note that if your grep command supports the -P option you may be able to use the Perl regular expression as-is for the second test.
this is almost it. bash has no expression for multiple digits.
#!/bin/bash
command=( grep 'Stage ' "$hostlog" )
while read line
do
[ "$line" != "${line/Stage [0-9]/}" ] && (( ++stage_number ))
done < <( "${command[#]}" )
On the other hand taking the function of the perl script into account rather than the operations it performs the whole thing could be rewritten as
(( stage_number += ` grep -c 'Stage \d\+\s' "$hostlog" ` ))
or this
stage_number=` grep -c 'Stage \d\+\s' "$hostlog" `
if, in the original perl, stage_number is uninitialised, or is initalised to 0.
I found some command line with Perl that inserts headers into my files without going through the tedious process of inserting them one by one. Can someone walk me through the Perl aspect of this command line? I'm new to this and can't seem to find the right explanations for what I wrote.
cat header.txt | perl -0 -i -pe 'BEGIN{$h = <STDIN>}; print $h' 1*
-e
rather than provide a script in a xxxx.pl file, provide it on the command line
-p
makes it iterate over filename arguments somewhat like sed but also prints the contents of $_ at the end of the script.
the two above are combined in -pe
-i
indicate you want to edit the file in place and write the output to the same file. In practice, Perl renames the input file and reads from this renamed version while writing to a new file with the original name
-0
redefines the end of record character (\n by default) so that you can read the entire input file as a single line
1*
is the command line argument to your script, so I guess you are modifying any file with a name that starts with 1 (you could have used *.c, or whatever depending on the type of files you are trying to modify)
print $h
prints the variable $h that is the "main" of your script. if it was initialized with the content of the header file (the intent of this one-liner) then it will print the header file
BEGIN{ some code here }
this is stuff you execute before the script starts. this is where I'm stumped. this doesn't seem like valid perl code
so basically:
this will supposedly slurp the entire header file (because of -0) in the BEGIN block and store it in the variable $h
iterate over all the files specified by the wildcards at the end of the command line
for each file: print the header (print $h) then print hte file itself (because of -pe)
so it's equivalent to spelling the script out:
$h = gets content of the entire header file
while (<>){ #loop implied by -pe, iterates over all the 1* files
# the main contents of the "-e" script are inserted below as part of executing -pe
print h$; #print the header we saved
print $_; # implied by -pe, and since we are using -0, this prints the entire content in one shot
# end of the "-e" script. again it was a single print $h statement, the second print is implied by -pe
}
It's a bit hard to explain, take a look at the perlrun documentation for details (run man perlrun).
This is not 100% complete explanation because I don;t think the BEGIN block is right. I tried it on my ubuntu machine and it complained about its syntax too
Here's something similar, with an explanation. The program in the question doesn't run on my mac.
I needed to add the #nullable disable directive to the top of all my csharp files as part of migrating to nullable reference types.
perl -w -i -p -0777 -e 's/^/#nullable disable\n\n/' $(find . -iname '*.cs')
-w enable warnings
-i edit files in place
-p read each file block by block, printing each block after applying a perl expression. the default block size is one line
-0777 changes the default block size to the entire file
-e the perl expression to execute
The final argument uses shell command substitution to create a list of files. It passes that list of file paths to the perl command. The find command searches for files that end in .cs.
The perl program is a single substitution command. It matches the very beginning of the block and replaces (prepends, really) with "#nullable disable" and a couple new-lines.
I'm trying to read a specific section of a line out of a file with Perl.
The file in question is of the following syntax.
# Sets $USER1$
$USER1$=/usr/....
# Sets $USER2$
#$USER2$=/usr/...
My oneliner is simple,
perl -ne 'm/^\$USER1\$\s*=\s*(\S*?)\s*$/m; print "$1";' /my/file
For some reason I'm getting the extraction for $1 repeated several times over, apparently once for every line in the file after my match occurs. What am I missing here?
You are executing print for every line of the file because print gets called for every line, whether the regex matches or not. Replace the first ; with an &&.
From perlre:
NOTE: Failed matches in Perl do not reset the match variables, which makes it easier to write code that tests for a series of more specific cases and remembers the best match.
Try this instead:
perl -ne 'print "$1" if m/^\$USER1\$\s*=\s*(\S*?)\s*$/m;' /my/file
$ cat test.txt
# Sets $USER1$
$USER1$=/usr/....
# Sets $USER2$
#$USER2$=/usr/...
$ perl -nle 'print if /^\$USER1/;' test.txt
$USER1$=/usr/....
Try this
perl -ne '/^.*1?=([\w\W].*)$/;print "$1";' file
I am writing the following command to extract the text in makefile:-
#awk '/Exported Layer/,/Total Polygons/' out_compare.err | perl -lane '$el=$F[3] if(/Exported Layer/); print "$el: $f[3]" if (/Total Polygons/);' | cat
But it is giving the following error:-
Can't modify constant item in scalar assignment at -e line 1, near "] if"
Execution of -e aborted due to compilation errors.
Would you guys like to suggest something? :-)
Make is oblivious to shell quoting in commands, so the $ characters in your Perl snippet are being interpreted as make variables $e and $F. These variables don't exist in your makefile and are being expanded as empty, leading to the Perl syntax errors you're seeing.
You need to escape the $ characters from make like this:
... perl -lane '$$el=$$F[3] if(/Exported Layer/); ...
See also the GNU Make manual.
I have a variable in a shell script,
var=1234_number
I want to replace all other than integer of $var .. how can I do it using a perl onliner?
You might be looking for something to edit the shell script, in which case, this might be sufficient:
perl -i.bak -e 's/\b(var=\d+).*/$1/' shellscript.sh
The '-i' overwrites the original file, saving a copy in shellscript.sh.bak; the substitute command finds assignments to 'var' (and not any longer name ending 'var') followed by an equals sign, some digits, and any non-digits, and leaves behind just the assignment of digits.
In the example, it gives:
var=1234
Note that the Perl regex is not foolproof - it will mangle this (dropping the closing brace).
: ${var=1234_number}
Dealing with all such possible variants is extremely fairly tricky:
echo $var=$other
OTOH, you might be looking to eliminate digits from a variable within a shell script, in which case:
var=$(echo $var | perl -e 's/\D//g')
You could also use 'sed' for the job:
var=$(echo $var | sed 's/[^0-9]//g')
No need to use anything but the shell for this
var=1234_abcd
var=${var%_*}
echo $var # => 1234
See 'Parameter Expansion' in the bash manual.