Background: I have a fairly simple bash script that I'm using to generate a CSV log file. As part of that bash script I poll other devices on my network using netcat. The netcat command returns a stream of information that I can pipe that into a grep command to get to certain values I need in the CSV file. I save that return value from grep into a bash variable and then at the end of the script, I write out all saved bash variables to a CSV file. (Simple enough.)
The change I'd like to make is the amount of netcat commands I have to issue for each piece of information I want to save off. With each issued netcat command I get ALL possible values returned (so each time returns the same data and is burdensome on the network). So, I'd like to only use netcat once and parse the return value as many times as I need to create the bash variables that can later be concatenated together into a single record in the CSV file I'm creating.
Specific Question: Using bash syntax if I pass the output of the netcat command to a file using > (versus the current grepmethod) I get a file with each entry on its own line (presumably separated with the \n as the EOL record separator -- easy for perl regex). However, if I save the output of netcat directly to a bash variable, and echo that variable, all of the data is jumbled together, so it is cumbersome to parse out (not so easy).
I have played with two options: First, I think a perl one-liner may be a good solution here, but I'm not sure how to best execute it. Pseudo code might be to save the netcat output to a a bash variable and then somehow figure out how to parse it with perl (not straight forward though).
The second option would be to use bash's > and send netcat's output to a file. This would be easy to process with perl and Regex given the \n EOL, but that would require opening an external file and passing it to a perl script for processing AND then somehow passing its return value back into the bash script as a bash variable for entry into the CSV file.
I know I'm missing something simple here. Is there a way I can force a newline entry into the bash variable from netcat and then repeatedly run a perl-one liner against that variable to create each of the CSV variables I need -- all within the same bash script? Sorry, for the long question.
The second option would be to use bash's > and send netcat's output to
a file. This would be easy to process with perl and Regex given the \n
EOL, but that would require opening an external file and passing it to
a perl script for processing AND then somehow passing its return value
back into the bash script as a bash variable for entry into the CSV
file.
This is actually a fairly common idiom: save the output from netcat in
a temporary file, then use grep or awk or perl or what-have-you as
many times as necessary to extract data from that file:
# create a temporary file and arrange to have it
# deleted when the script exists.
tmpfile=$(mktemp tmpXXXXXX)
trap "rm -f $tmpfile" EXIT
# dump data from netcat into the
# temporary file.
nc somehost someport > $tmpfile
# extract some information into variable `myvar`
myvar=$(awk '/something/ {print $4}' $tmpfile)
That last line demonstrates how to get the output of something (in this case, an awk script) into a variable. If you were using perl to extract some information you could do the same thing.
You could also just write the whole script in perl, which might make your life easier.
Related
I am working on creating some training material where I am using perl. One of the things I want to do is have the scripts be set up for the student correctly, regardless of where they extra the compressed files. I am working on a Windows batch file that will copy the perl templates to the working location and then update path in the copy of the perl template files to the correct location. The perl template have this as the first line:
#!_BASE_software/perl/bin/perl.exe
The batch file looks like this:
SET TRAINING=%~dp0
copy %TRAINING%\template\*.pl %TRAINING%work
%TRAINING%software\perl\bin\perl -pi.bak -e 's/_BASE_/%TRAINING%/g' %TRAINING%work\*.pl
I have a few problems with this:
Perl doesn't seem to like the wildcard in the filename
It turns out that %TRAINING% is going to expand into a string with backslashes which need to be converted into forwardslashes and needs to be escaped within the regex.
How do I fix this?
First of all, Windows doesn't use the shebang line, so I'm not sure why you're doing any of this work in the first place.
Perl will read the shebang line and look for options if perl is found in the path, even on Windows, but that means that #!perl is sufficient if you want to pass options via the shebang line (e.g. #!perl -n).
Now, it's possible that you use Cygwin, MSYS or some other unix emulation instead of Windows to run the program, but you are placing a Windows path in the shebang line (C:...) rather than a unix path, so that doesn't make sense either.
There are three additional problems with the attempt:
cmd uses double-quotes for quoting.
cmd doesn't perform wildcard expansion like sh, so it's up to your program do it.
You are trying to generate Perl code from cmd. ouch.
If we go ahead, we get:
"%TRAINING%software\perl\bin\perl" -MFile::DosGlob=glob -pe"BEGIN { #ARGV = map glob, #ARGV; $base = $ENV{TRAINING} =~ s{\\}{/}rg } s/_BASE_/$base/g" -i.bak -- %TRAINING%work\*.pl
If we add line breaks for readability, we get the following (that cmd won't accept):
"%TRAINING%software\perl\bin\perl"
-MFile::DosGlob=glob
-pe"
BEGIN {
#ARGV = map glob, #ARGV;
$base = $ENV{TRAINING} =~ s{\\}{/}rg
}
s/_BASE_/$base/g
"
-i.bak -- %TRAINING%work\*.pl
I'm fairly new to the whole coding game, and am very grateful for every answer!
I am working on a directory with many .txt files in them and have a file with looong list of regex like "perl -p -i -e 's/\n\n/\n/g' *.xml" they all work if I copy them to terminal. But is there a possibility to run them straight from the file?
I tried ./unicode.sh but that resulted in:
No such file or directory.
Any ideas?
Thank you so much!
Here's a (mostly) equivalent Perl script to the oneliner perl -p -i -e 's/\n\n/\n/g' *.xml (one main difference being that this has strict and warnings enabled, which is strongly recommended), which you could expand upon by putting more code to modify the current line in the body of the while loop.
#!/usr/bin/env perl
use warnings;
use strict;
if (!#ARGV) { # if no files on command line
#ARGV = glob('*.xml'); # get a default list of files
}
local $^I = ''; # enable inplace editing (like perl -i)
while (<>) { # read each line of each file into $_
s/\n\n/\n/g; # modify $_ with a regex
# more regexes here...
print; # write the line $_ back out
}
You can save this script in a file such as process.pl, and then run it with perl process.pl, or do chmod u+x process.pl and then run it via ./process.pl.
On the other hand, you really shouldn't modify XML files with regular expressions, there are lots of Perl modules to do XML processing - I wrote about that some more here. Also, in the example you showed, s/\n\n/\n/g actually won't have any effect, since when reading files line-by-line, no string will contain two \n's (you can change how Perl reads files, but I don't see any mention of that in the question).
Edit: You've named the script in your example unicode.sh - if you're processing Unicode files, then Perl has very powerful features to help with that, although the code won't necessarily end up as nice and short as I've showed above. You'll have to tell us some more about what you're doing, and show some example input and output, to get suggestions about that. See also e.g. perlunitut.
It's likely if you got no such file or directory, your problem was you forgot to make unicode.sh executable, as in chmod +x unicode.sh, assuming that's a script that you wrote.
Of course the normal way to run multiple perl commands is this thing that looks like runme.pl which you write, i.e., a perl script.
That said, yes, everything will work from the terminal, you just need to be careful about escaping that bash performs.
I am very new to shell scripting and trying to learn the "sed" command functionality.
I have a file called configurations.txt with some variables defined in it with some string values initialised to each of them.
I am trying to replace a string in a file (values.txt) which is present in some other directory by the values of the variables defined. The name of the file is values.txt.
Data present in configurations.txt:-
mem="cpu.memory=4G"
proc="cpu.processor=Intel"
Data present in the values.txt (present in /home/cpu/script):-
cpu.memory=1G
cpu.processor=Dell
I am trying to make a shell script called repl.sh and I dont have alot of code in it for now but here is what I got:-
#!/bin/bash
source /home/configurations.txt
sed <need some help here>
Expected output is after an appropriate regex applied, when I run script sh repl.sh, in my values.txt , It must have the following data present:-
cpu.memory=4G
cpu.processor=Intell
Originally which was 1G and Dell.
Would highly appreciate some quick help. Thanks
This question lacks some sort of abstract routine and looks like "help me do something concrete please". Thus it's very unlikely that anyone would provide a full solution for that problem.
What you should do try to split this task into number of small pieces.
1) Iterate over configuration.txt and get values from each line. To do that you need to get X and Y from a value="X=Y" string.
This regex could be helpful here - ([^=]+)=\"([^=]+)=([^=]+)\". It contains 3 matching groups separated by ". For example,
>> sed -r 's/([^=]+)=\"([^=]+)=([^=]+)\"/\1/' configurations.txt
mem
proc
>> sed -r 's/([^=]+)=\"([^=]+)=([^=]+)\"/\2/' configurations.txt
cpu.memory
cpu.processor
>> sed -r 's/([^=]+)=\"([^=]+)=([^=]+)\"/\3/' configurations.txt
4G
Intel
2) For each X and Y find X=Z in values.txt and substitute it with a X=Y.
For example, let's change cpu.memory value in values.txt with 4G:
>> X=cpu.memory; Y=4G; sed -r "s/(${X}=).*/\1${Y}/" values.txt
cpu.memory=4G
cpu.processor=Dell
Use -i flag to do changes in place.
Here is an awk based answer:
$ cat config.txt
cpu.memory=4G
cpu.processor=Intel
$ cat values.txt
cpu.memory=1G
cpu.processor=Dell
cpu.speed=4GHz
$ awk -F= 'FNR==NR{a[$1]=$2; next;}; {if($1 in a){$2=a[$1]}}1' OFS== config.txt values.txt
cpu.memory=4G
cpu.processor=Intel
cpu.speed=4GHz
Explanation: First read config.txt & save in memory. Then read values.txt. If a particular value was defined in config.txt, use the saved value from memory (config.txt).
This question already has answers here:
Extract filename and extension in Bash
(38 answers)
Closed 8 years ago.
i have a script that is pushing out some filesystem data to be uploaded to another system.
it would be very handy if i could tell myself what 'kind' of file each file actually is, because it will help with some querying later on down the road.
so, for example, say that my script is spitting out the following:
/home/myuser/mydata/myfile/data.log
/home/myuser/mydata/myfile/myfile.gz
/home/myuser/mydata/myfile/mod.conf
/home/myuser/mydata/myfile/security
/home/myuser/mydata/myfile/last
in the end, i'd like to see:
/home/myuser/mydata/myfile/data.log log
/home/myuser/mydata/myfile/myfile.gz gz
/home/myuser/mydata/myfile/mod.conf conf
/home/myuser/mydata/myfile/security security
/home/myuser/mydata/myfile/last last
there's gotta be a way to do this with regular expressions and sed, but i can't figure it out.
any suggestions?
EDIT:
i need to get this info via the command line. looking at the answers so far, i obviously have not made this clear. so with the example data i provided, assume that data is all being fed via greps and seds (data is already sterlized). i need to be able to pipe the example data to sed/grep/awk/whatever in order to produce the desired results.
Print last filed that are separated by a none alpha character.
awk -F '[^[:alpha:]]' '{ print $0,$NF }'
/home/myuser/mydata/myfile/data.log log
/home/myuser/mydata/myfile/myfile.gz gz
/home/myuser/mydata/myfile/mod.conf conf
/home/myuser/mydata/myfile/security security
/home/myuser/mydata/myfile/last last
This should work for you:
x='/home/myuser/mydata/myfile/security'
( IFS=[/.] && arr=( $x ) && echo ${arr[#]:(-1):1} )
security
x='/home/myuser/mydata/myfile/data.log'
( IFS=[/.] && arr=( $x ) && echo ${arr[#]:(-1):1} )
log
To extract the last element in a filename path:
filename=$(path##*/}
To extract characters after a dot in a filename:
extension=${filename##*.}
But (my comment) rather than looking at the extension, it might be better to use file. See man file.
As others have already answered, to parse the file names:
extension="${full_file_name##*.}" # BASH and Kornshell/POSIX only
filename=$(basename "$full_file_name")
dirname=$(dirname "$full_file_name")
Quotes are needed if file names could have spaces, tabs, or other strange characters in them.
You can also test whether a file is a directory or file or link with the test command (which is linked to [ so that test -f foo is the same as [ -f foo ].
However, you said: "it would be very handy if i could tell myself what kind of file each file actually is".
In that case, you may want to investigate the file command. This command will return the file type as determined by some sort of magic file (traditionally in /etc/magic), but newer implementations can use the user's own scheme. This can tell file type by extension and by the magic number in the file's header, or by looking at the first few lines in the file (looking for a regular expression ^#! .*/bash$ in the first line.
This extracts the last component after a slash or a dot.
awk -F '[/.]' '{ print $NF }'
I'm working on refactoring a bunch of PHP code for an instructor. The first thing I've decided to do is to update all the SQL files to be written in Drupal SQL coding conventions, i.e., to have all-uppercase keywords. I've written a few regular expressions:
:%s/create table/CREATE TABLE/gi
:%s/create database/CREATE DATABASE/gi
:%s/primary key/PRIMARY KEY/gi
:%s/auto_increment/AUTO_INCREMENT/gi
:%s/not null/NOT NULL/gi
Okay, that's a start. Now I just open every SQL file in Vim, run all five regular expressions, and save. This feels like five times the work it should be. Can they be compounded in to one obnoxiously long but easily copy-pastable regex?
why do you have to do it in vim? how about sed/awk?
e.g. with sed
sed -e 's/create table/\U&/g' -e's/not null/\U&/g' -e 's/.../\U&/' *.sql
btw, in vi you may do
:%s/create table/\U&/g
to change case, well save some typing.
update
if you really want a long command to execute in vi, maybe you could try:
:%s/create table\|create database\|foo\|bar\|blah/\U&/g
Open the file containing that substitution commands.
Copy its contents (to the unnamed register, by default):
:%y
If there is only one file where the substitutions should be
performed, open it as usual and run the contents of that register
as a Normal mode command:
:#"
If there are several files to edit automatically, open those
files as arguments:
:args *.sql
Execute the yanked substitutions for each file in the argument list:
:argdo #"|up
(The :update command running after the substitutions, writes
the buffer to file if it has been changed.)
While sed can handle what you want (hovewer it can be interactive as you requestred by flag 'i'), vim still much powerfull. Once I needed to change last argument in some function call in 1M SLOC code base. The arguments could be in one line or in several lines. In vim I achieved it pretty easy.
You can open all php files in vim at once:
vim *.php
After that run in ex mode:
:bufdo! %s/create table/CREATE TABLE/gi
Repeat the rest of commands. At the end save all the files and exit vim:
:xall