I am trying to put the system command like below to the perl script, but
sed expression contains both quotes and backticks and I am not sure how to escape all of them, so it will execute my system command exactly as I need.
Here is the example of the command:
mysql -u root -D porta-billing -e "..." | sed "s/'/\'/;s/\t/\",\"/g;s/^/\"/;s/$/\"/;s/\n//g"
The answer to the question you're asking is to use the qx(...) operator. qx(...) is the "choose your own delimiter" version of backticks.
my $output = qx[ ... ];
Or
my $output = qx( ... );
Or
my $output = qx! ... !;
It's easy to find a delimiter that won't clash with the characters in your command string.
But the answer to the question that you should be asking has two parts:
Don't call mysql from your Perl program - use DBI instead.
Don't call sed from your Perl program - use Perl code to manipulate your text.
I feel slightly nervous about the first part of my answer as I'm worried you will just take my hacky workaround and end up with an unmaintainable mess. Please take note of the advice in the second half - even if you ignore it in this case.
How can I use this code to create more commands. The current version does 2. How can i do 3 or 4 or more?
my $startprocess = `(echo "y" | nohup myprocess) &`
The original question answered by user DVK:
Can I execute a multiline command in Perl's backticks?
edit: thanks for the reply sebastian.
I have to run everything in one line because Im running a program within terminal and i want to make progressive commands.
e.g command 1 starts the program. command 2 navigates me to the menu. Command 3 lets me change a setting. Command 4 lets me issue a command that prompts a response that I can only get under the condition of that new setting.
To run multiple commands would keep me trapped in step one.
The line you quoted contains one command line piped together. That's not running multiple commands.
Did you consider using open?
my $pid = open my $fh, '-|', 'myprocess';
print $fh "y\n";
There is no need to run multiple commands in one (backtick) line, why not just use multiple ones?
$first = `whoami`;
$second = `uptime`;
$third = `date`;
Backticks are used to capture the output of the command, system just runs the command and returns the exit state:
system '(echo "y" | nohup myprocess) &';
All solutions allow multiple commands piped together as this is a shell feature and all commands just pass the command string to the shell (unless it's simple enough to handle it without a shell):
Bash:
$ ps axu|grep '0:00'|sort|uniq -c|wc
Perl:
system "ps axu|grep '0:00'|sort|uniq -c|wc";
$result = `ps axu|grep '0:00'|sort|uniq -c|wc`;
open my $fh, '|-', "ps axu|grep '0:00'|sort|uniq -c|wc";
Always watch the quotation marks: system "foo "bar" baz"; won't pass "bar" baz as arguments to the foo command.
Lots of common stuff in this answer: Please be more detailed in your question to get a better reply.
I have a question about how to execute the perl file inside of a shell script
I have 2 files now, "test.sh" and "test.pl", here are example of my scripts
SHELL script
#!/bin/bash
perl FILEPATH/test.pl
......
PERL script
#!/usr/bin/perl
my $a = "hello"
sub saysomething
{
print $a;
}
.....
The way I call the shell script is : under the path of shell scripts, execute "./test.sh"
All mentioned above are working under the environment
GUN bash, version 4.2.24(1)-release (i686-pc-linux-gnu) + perl (v5.14.2)
But if I put those scripts on server (which I couldn't change the bash / perl version)
GNU bash, version 4.2.10(1)-release (x86_64-pc-linux-gnu) + perl (v5.12.4), I got the followign message:
FILEPATH/test.pl: line 2: my: command not found
Does anybody know how can I solve this problem?
BTW, if I execute the perl script individually (perl FILEPATH/FILENAME.pl), it works perfectly.
In order to execute a perl script by .sh script you dont need to use perl prefix, but only:
#!/bin/sh
/somewhere/perlScript.pl
It will work without problem.
This problem is at least two-fold. One, you have to have the location of Perl in your environment PATH. Two, the location of Perl may be different on different machines. One solution to both problems that I, and others, have used for years is to make use of a "magic header" of some sort at the top of Perl programs. The header identifies itself as a sh shell script and leverages the fact that /bin/sh exists in every version/flavor of Linux/UNIX. The header's job is to fortify the PATH with various possible Perl locations and then run the Perl script in place of itself (via exec). Here is a "Hello World" example:
1 #! /bin/sh --
2 eval '(exit $?0)' && eval 'PERL_BADLANG=x;PATH="/usr/bin:/bin:/usr/local/bin:$PATH";export PERL_BADLANG;: \
3 ;exec perl -x -S -- "$0" ${1+"$#"};#'if 0;
4 exec 'setenv PERL_BADLANG x;exec perl -x -S -- "$0" $argv:q;#'.q
5 #!/bin/perl -w
6 +($0=~/(.*)/s);do(index($1,"/")<0?"./$1":$1);die$#if$#;__END__+if 0;
7 # Above is magic header ... real Perl code begins here
8 use strict;
9 use warnings;
10 print "hello world!\n";
Note: I added line numbers just to make it clear where lines start and end.
First check where perl is installed on your system, e.g. which perl and use that location in the shebang line instead of /usr/bin/perl, if it is different.
If all other recommendations fail, check the first line of the script on the machine where it is not running properly by doing this: head -1 test.pl | xxd. Does the output show the last two bytes as 0d 0a? If so, you probably copied over the file via Windows and didn't do a dos2unix conversion.
"command not found" is an error emitted by the shell. You are trying to run your Perl script by the shell, not by Perl.
I want to use gnuplot to draw figure from data file, say foo.data. Currently, I hardcoded the data file name in the command file, say foo.plt, and run command gnuplot foo.plg to plot data. However, I want to pass the data file name as a command argument, e.g. running command gnuplot foo.plg foo.data. How to parse the command line arguments in gnuplot script file? Thanks.
You can input variables via switch -e
$ gnuplot -e "filename='foo.data'" foo.plg
In foo.plg you can then use that variable
$ cat foo.plg
plot filename
pause -1
To make "foo.plg" a bit more generic, use a conditional:
if (!exists("filename")) filename='default.dat'
plot filename
pause -1
Note that -e has to precede the filename otherwise the file runs before the -e statements. In particular, running a shebang gnuplot #!/usr/bin/env gnuplot with ./foo.plg -e ... CLI arguments will ignore use the arguments provided.
You can pass arguments to a gnuplot script since version 5.0, with the flag -c. These arguments are accessed through the variables ARG0 to ARG9, ARG0 being the script, and ARG1 to ARG9 string variables. The number of arguments is given by ARGC.
For example, the following script ("script.gp")
#!/usr/local/bin/gnuplot --persist
THIRD=ARG3
print "script name : ", ARG0
print "first argument : ", ARG1
print "third argument : ", THIRD
print "number of arguments: ", ARGC
can be called as:
$ gnuplot -c script.gp one two three four five
script name : script.gp
first argument : one
third argument : three
number of arguments: 5
or within gnuplot as
gnuplot> call 'script.gp' one two three four five
script name : script.gp
first argument : one
third argument : three
number of arguments: 5
In gnuplot 4.6.6 and earlier, there exists a call mechanism with a different (now deprecated) syntax. The arguments are accessed through $#, $0,...,$9. For example, the same script above looks like:
#!/usr/bin/gnuplot --persist
THIRD="$2"
print "first argument : ", "$0"
print "second argument : ", "$1"
print "third argument : ", THIRD
print "number of arguments: ", "$#"
and it is called within gnuplot as (remember, version <4.6.6)
gnuplot> call 'script4.gp' one two three four five
first argument : one
second argument : two
third argument : three
number of arguments: 5
Notice there is no variable for the script name, so $0 is the first argument, and the variables are called within quotes. There is no way to use this directly from the command line, only through tricks as the one suggested by #con-fu-se.
You can also pass information in through the environment as is suggested here. The example by Ismail Amin is repeated here:
In the shell:
export name=plot_data_file
In a Gnuplot script:
#! /usr/bin/gnuplot
name=system("echo $name")
set title name
plot name using ($16 * 8):20 with linespoints notitle
pause -1
The answer of Jari Laamanen is the best solution. I want just explain how to use more than 1 input parameter with shell variables:
output=test1.png
data=foo.data
gnuplot -e "datafile='${data}'; outputname='${output}'" foo.plg
and foo.plg:
set terminal png
set outputname
f(x) = sin(x)
plot datafile
As you can see,more parameters are passed with semi colons (like in bash scripts), but string variables NEED to be encapsuled with ' ' (gnuplot syntax, NOT Bash syntax)
You may use trick in unix/linux environment:
in gnuplot program: plot "/dev/stdin" ...
In command line: gnuplot program.plot < data.dat
This question is well answered but I think I can find a niche to fill here regardless, if only to reduce the workload on somebody googling this like I did. The answer from vagoberto gave me what I needed to solve my version of this problem and so I'll share my solution here.
I developed a plot script in an up-to-date environment which allowed me to do:
#!/usr/bin/gnuplot -c
set terminal png truecolor transparent crop
set output ARG1
set size 1, 0.2
rrLower = ARG2
rrUpper = ARG3
rrSD = ARG4
resultx = ARG5+0 # Type coercion required for data series
resulty = 0.02 # fixed
# etc.
This executes perfectly well from command-line in an environment with a recent gnuplot (5.0.3 in my case).
$ ./plotStuff.gp 'output.png' 2.3 6.7 4.3 7
When uploaded to my server and executed, it failed because the server version was 4.6.4 (current on Ubuntu 14.04 LTS).
The below shim solved this problem without requiring any change to the original script.
#!/bin/bash
# GPlot v<4.6.6 doesn't support direct command line arguments.
#This script backfills the functionality transparently.
SCRIPT="plotStuff.gp"
ARG1=$1
ARG2=$2
ARG3=$3
ARG4=$4
ARG5=$5
ARG6=$6
gnuplot -e "ARG1='${ARG1}'; ARG2='${ARG2}'; ARG3='${ARG3}'; ARG4='${ARG4}'; ARG5='${ARG5}'; ARG6='${ARG6}'" $SCRIPT
The combination of these two scripts allows parameters to be passed from bash to gnuplot scripts without regard to the gnuplot version and in basically any *nix.
You could even do some shell magic, e.g. like this:
#!/bin/bash
inputfile="${1}" #you could even do some getopt magic here...
################################################################################
## generate a gnuplotscript, strip off bash header
gnuplotscript=$(mktemp /tmp/gnuplot_cmd_$(basename "${0}").XXXXXX.gnuplot)
firstline=$(grep -m 1 -n "^#!/usr/bin/gnuplot" "${0}")
firstline=${firstline%%:*} #remove everything after the colon
sed -e "1,${firstline}d" < "${0}" > "${gnuplotscript}"
################################################################################
## run gnuplot
/usr/bin/gnuplot -e "inputfile=\"${inputfile}\"" "${gnuplotscript}"
status=$?
if [[ ${status} -ne 0 ]] ; then
echo "ERROR: gnuplot returned with exit status $?"
fi
################################################################################
## cleanup and exit
rm -f "${gnuplotscript}"
exit ${status}
#!/usr/bin/gnuplot
plot inputfile using 1:4 with linespoints
#... or whatever you want
My implementation is a bit more complex (e.g. replacing some magic tokens in the sed call, while I am already at it...), but I simplified this example for better understanding.
You could also make it even simpler.... YMMV.
In the shell write
gnuplot -persist -e "plot filename1.dat,filename2.dat"
and consecutively the files you want.
-persist is used to make the gnuplot screen stay as long as the user doesn't exit it manually.
#vagoberto's answer seems the best IMHO if you need positional arguments, and I have a small improvement to add.
vagoberto's suggestion:
#!/usr/local/bin/gnuplot --persist
THIRD=ARG3
print "script name : ", ARG0
print "first argument : ", ARG1
print "third argument : ", THIRD
print "number of arguments: ", ARGC
which gets called by:
$ gnuplot -c script.gp one two three four five
script name : script.gp
first argument : one
third argument : three
number of arguments: 5
for those lazy typers like myself, one could make the script executable (chmod 755 script.gp)
then use the following:
#!/usr/bin/env gnuplot -c
THIRD=ARG3
print "script name : ", ARG0
print "first argument : ", ARG1
print "third argument : ", THIRD
print "number of arguments: ", ARGC
and execute it as:
$ ./imb.plot a b c d
script name : ./imb.plot
first argument : a
third argument : c
number of arguments: 4
Yet another way is this:
You have a gnuplot script named scriptname.gp:
#!/usr/bin/gnuplot -p
# This code is in the file 'scriptname.gp'
EPATH = $0
FILENAME = $1
plot FILENAME
Now you can call the gnuplot script scriptname.gp by this convoluted peace of syntax:
echo "call \"scriptname.gp\" \"'.'\" \"'data.dat'\"" | gnuplot
I need to get an example file file from a find command in a Perl script to create another system call afterwards. For some reason, the find command gets stuck when I call it from the script. Here is what I need to do:
my $search_dir = "/something/like/this/??/??/??";
# the triple '??' are needed here
my $cmd = "find $search_dir -name \"\*.$var1.token1.$var2.ext\" | head -n 1";
my $first_example_file = `$cmd`; chomp $first_example_file;
This gets stuck when I run it through Perl, it never finishes executing the command, whereas the constructed $cmd runs in no time if I copy+paste it and run in in my bash terminal. Any ideas?
Try using the File::Find perl module for finding files. If you would like to use bash's find in your perl then you might have to use $(..) in your command.
I am not in to perl … just trying to help out.
Update:
As stated in the comments by Rohaq you can also use File::Find::Rule
I'd wager globbing (shell metacharacter expansion) is involved. But regardless, try and chop the command up. Does it work without the pipe? What about without the ?? in the pathname? What happens if you prepend 'echo' ("echo find ...")? Still hanging? Then you can try it under perl -d - the debugger; perldoc perldebug is your friend.