Questions specific to GNU’s Bourne Again SHell, as opposed to other Bourne/POSIX shells. For questions about Unix shells in general, use the /shell tag instead.

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1
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3answers
2k views

Split XML file into multiple files

I have an xml file that have different nodes, I want to split files like this: <unix> <mm> </unix> <osx> <nn> </osx> When I run the script I want it to make ...
5
votes
1answer
387 views

Why different behaviour of trapping EXIT vs INT

Running bash 4.3 on Kubuntu Trusty 64 bit. Please see the following two files: trapping-int.sh #! /bin/bash trap "echo Exiting" INT cat </dev/urandom >/dev/null echo Hello trapping-exit.sh ...
2
votes
4answers
437 views

Mute system error message in a script file and display mine

I have created a simple script to move all the files with .sh suffix in the current working directory to a designated directory If there was no such file, the script should output only an error ...
0
votes
0answers
108 views

Why is a here-string command substitution considered as a single line?

I'm experimenting with while read syntax and there is a thing I don't understand. The most basic scenario which reproduces the problem is the following: a bash script a.sh calls another script b.sh ...
9
votes
1answer
775 views

Why does BASH process substitution not work with some commands?

On occasion process substitution will not work as expected. Here is an example: Input: gcc <(echo 'int main(){return 0;}') Output: /dev/fd/63: file not recognized: Illegal seek collect2: ...
6
votes
1answer
329 views

Does bash return anything when it runs a command?

I was found the guide to test if there is a bug in Bash. Namely, when x='() { :;}; echo VULNERABLE' bash -c x does not return anything, it is vulnerable. But are there cases like in C that bash ...
0
votes
1answer
406 views

Back-up script via bash — issues with file paths?

I'm trying to run a back-up bash script in via Plesk scheduled tasks on a CentOS GoDaddy Managed Dedicated Server. I'm having a frustrating amount of trouble with this (made worse by the fact that it ...
5
votes
5answers
4k views

How do I use the “if” command for multiple conditions?

How do I do this? if [ -f town-*.swf ] then mkdir towns fi This checks if town-*.swf exists, but I also need it to look for city-*.swf among others, so I need something like this: if [ -f ...
10
votes
2answers
4k views

Exclude one pattern from glob match

I have several files with the same base filename. I'd like to remove all but one foo.org #keep foo.tex #delete foo.fls #delete foo.bib #delete etc If I didn't need to keep one, I know I could use ...
3
votes
1answer
196 views

What is the purpose of those special characters in the sed command? [closed]

I found this bash command that creates a directory tree in your console window. I find it quite useful, but I don't really understand how all of the special characters work. Could someone help break ...
-1
votes
1answer
109 views

How to insert the entry into the newline?

I have the following entry in a tab delimited file test1.txt key1 10|15 20 30 11|xx 21 31 key2 527|240 269 0 0 0 2462 546 281 0 0 Is there any way I can transform this file into the below format? I ...
10
votes
6answers
16k views

Using jq to extract values and format in CSV

I have the below JSON file: { "data": [ { "displayName": "First Name", "rank": 1, "value": "VALUE" }, { "displayName": "Last Name", "rank": 2, ...
0
votes
1answer
121 views

route -n gives output “route: fscanf”

If I boot my system and no interface has an IP address I get the above output. However if I give an interface an IP, even if I remove it again, this will disappear. Why does this happen? Is it that ...
2
votes
3answers
97 views

Specifiy Unix TimeStamp Range in Parameter

I am launching a mrjob in bash and need to pass in as parameters a range of gz files which have unix time stamps in them as: filename_9127381923.gz. How to do this in the simplest possible way? I can ...
5
votes
1answer
366 views

Why does “cat /tmp/out1 > /tmp/in2 &” appear as “bash” with the “ps” command?

Consider: mkfifo /tmp/out1 mkfifo /tmp/in2 cat /tmp/out1 > /tmp/in2 & When I run ps it appears as bash in the CMD section. Why?
3
votes
1answer
750 views

PHP CLI and Bash - change behaviour of PHP keyword

Our hosting providers have installed 3 versions of PHP onto our linux box and when I SSH into it the command php points to use/bin/php which is version 5.2, the command php-5.4 points to ...
5
votes
1answer
558 views

While command not found and syntax error near unexpected token [closed]

I am trying to write a shell script that takes a string input from a user, asks for a file name and reports whether that string is present in the file. Below is my current script. #!/bin/bash while ...
3
votes
2answers
48 views

Help with iterating fieldA in CSV file, where fieldB has specified value

I've been trying to setup a script to run on gitbash, to process a CSV file so each record that has a specific value, the last field is changed from empty ("") to a value that iterates from 1 to 16. ...
2
votes
2answers
1k views

Bash script to verify that an rpm is at least at a given version

I need to write a script to verify that an RPM is at least a given version in Linux. QUESTION 1: How can I get the RPM version in a variable $RPM_VERSION, so that it contains the version all the way ...
3
votes
1answer
312 views

How do I stop screen from clobbering my titles?

I am using bash and GNU screen on centos7. I notice that if I ssh to another server, change the title (via ctrl+a+A), and log out of the server that my new title gets overwritten by USER@HOST:~. How ...
3
votes
2answers
270 views

Is there a way to execute commands while getting user input?

I’m fairly new to scripting and I have a high-level question of how to do something. I want to design a simple game similar to space invaders, with these two main features for now: Bullets drop ...
1
vote
1answer
134 views

How to check PIPESTATUS equivalent during PROMPT_COMMAND execution?

I have a custom $PROMPT_COMMAND in bash that logs the last executed command and its return code. I was using $? for the latter happily until I realized that for piped commands this was insufficient. I ...
1
vote
2answers
2k views

RPM command stuck/FREEZE when installing RPM file

I want to install the following rpm from some reason RPM is stuck or freeze and not install the RPM package also I cant stop it by control C , please advice what could be the problem ? root]# rpm ...
6
votes
3answers
2k views

Control which process gets cancelled by Ctrl+C

I have a live CD that boots into Linux and runs a small Bash script. The script searches for and runs a second program (which is usually a compiled C++ binary). You're supposed to be able to abort ...
2
votes
1answer
342 views

Pipes & redirection binding precedence with disjuncts, conjuncts etc?

I know of the relative binding precedence of operators ‘;’, ‘&’, ‘&&’, or ‘||’ http://www.gnu.org/software/bash/manual/bashref.html#Lists but when pipes come into the picture along with ...
0
votes
1answer
55 views

How can I write a script which updates a text file?

I have made this script #PACKAGES.TXT array2=( `find . -type f -iname *t?z|awk '{print $1}'|cut -d / -f 3` ) funzioneZ() { echo -e " PACKAGE NAME: $i " } array3=( `find . -type f -iname *t?z|awk ...
2
votes
3answers
2k views

How long do the contents of the .bash_history file last?

How can I modify the contents of my bash_history file? What values or variables control how long the history lasts? Are there any other things I can change to provide finer control of my BASH ...
0
votes
2answers
2k views

How can I use netcat (nc) for chat client server model?

I am trying to write a daemon using bash. I will enter my partner's IP address and the connection will start using nc partner_ip 2015, likewise on the server I will start the connection using nc -l -p ...
0
votes
1answer
69 views

Howto adapt this bash construct to a sh valid construct

On converting some bash scripts to a platform where only /bin/sh is available i'm stumble about this bash construct: #!/bin/sh RSTPD=/sbin/rstpd RSTPCTL=/sbin/rstpctl RSTP=0 ...
4
votes
1answer
206 views

Is checking for exit status other than 0 after a `command || return` unreachable?

I am a shell script beginner and found the following patch of code: function some_fun() { #[...] [ -d ${MKAPP_BUILDDIR}/tmp ] || mkdir ${MKAPP_BUILDDIR}/tmp || return 1 if [ $? -ne 0 ]; ...
0
votes
1answer
116 views

Perl/awk/bash: multiply and sum values putting values inline instead original text [closed]

I have a text like this: ;--------------------------------------- JOURNEY_ARRAY_01 .BYTE <JOURNEY_00 .BYTE <JOURNEY_01 ;--------------------------------------- JOURNEY_ARRAY_03 ...
2
votes
2answers
216 views

An alias for a command to kill stopped jobs

I wanted to add an alias to my .bashrc so that I could kill all stopped jobs with a command like kill_stopped. I am aware that kill `jobs -p` can be used to accomplish this but I'd rather have an ...
2
votes
2answers
42 views

several virtual profiles for the same user

Many times there are several "identities" which one user uses: for work, open-source, academia etc., all require different ssh keys, editor configurations, git configs etc. I was wondering if there ...
1
vote
3answers
325 views

How to sum match numbers

I'm new at scripting, and need some help. Will appreciate your answers. I got this assignment, which is to find the sum of all five-digit numbers (in the range 10000 - 99999) containing exactly two ...
10
votes
4answers
587 views

Regular expression using \\ vs using \

Why does grep e\\.g\\. <<< "this is an e.g. wow" and grep e\.g\. <<< "this is an e.g. wow" do the same thing? If I add a third slash, it also has the same result. BUT, once I ...
0
votes
2answers
404 views

Why does this Shell script fail as cron job [closed]

I have the following in a shell script, when I run this script it works but when I put this as a cron job it does not work(nothing happens!). How come? script #!/bin/bash ...
8
votes
2answers
2k views

Is there a way to flatten a .pdf image from the command line?

In GIMP, I can import a .pdf, and use the GUI to flatten it (if it was made with many layers) by selecting "Flatten Image" in the "Image" dropdown menu. I can then export the .pdf with a new ...
1
vote
3answers
2k views

How to align a table of display nicely

I am trying to create a script that act as a ps command with it's own properties that I want to display. Say this is how processes would look like in ps command: sas 24431 1 0 Oct10 ? ...
1
vote
1answer
448 views

Append to PATH-like variable without creating leading colon if unset

I need to append a directory to PKG_CONFIG_PATH. Normally, I would use the standard export PKG_CONFIG_PATH=${PKG_CONFIG_PATH}:$(pyenv prefix)/lib/pkgconfig but PKG_CONFIG_PATH has not been ...
8
votes
2answers
925 views

How can a Bash script tell how it was run?

I have a Bash script I was trying to make to help me run a rather complex command with small changes that it would ask me about through echo and read. I have found solutions to force it to run a ...
0
votes
1answer
442 views

reading file using for, while - behavior

Consider the below scenario 2 vms - 192.168.229.131, 192.168.229.132 Both the vms has it's ip as 192.168.229.151 & 192.168.229.152 in it's /etc/hosts file Say there are around 50 vms like i ...
3
votes
1answer
726 views

What are the bash shell length limitations for here-docs?

What are the length limitations for using here-docs as part of bash command lines? I am finding that short here-docs work fine, but when they get longer there is some point or structure after which ...
1
vote
3answers
521 views

Random character generation - with random output!

This is what crunch can generate: [user@localhost ~] crunch 3 3 ab Crunch will now generate the following amount of data: 32 bytes 0 MB 0 GB 0 TB 0 PB Crunch will now generate the following number ...
2
votes
2answers
591 views

Environment variable not expanded inside the command line argument

I have a file user-pid.out2 which has "usernumber" and "process id" as two columns. based on usernumber I want to find corresponding process id. the first two lines below does not show the output ...
1
vote
2answers
101 views

How to perform command substitution before brace expansion

I would like to perform command substitution before brace expansion, but couldn't: $ ls {$(seq -s , 13 20)}.pdf ls: cannot access {13,14,15,16,17,18,19,20}.pdf: No such file or directory How can I? ...
1
vote
1answer
6k views

Is it possible to run two commands at the same time in a shell script?

I know that on the command line I can use & to run a command in the background. But I'm wondering if I can do it in a script. I have a script like this: date_stamp=$(date +"%Y-%m-%d" ...
1
vote
1answer
3k views

Bash error: “[y command not found” [duplicate]

I am trying to get this script to function correctly but I get ./passmark.sh line 7: [y command not found. Here is my script #!/bin/bash # A simple script to ask a user for a pass mark and then ...
1
vote
1answer
99 views

count matches and mismatches group by

Please help with a shell script of the following. I need count number of consistent variables in each lane (col1) across samples (col2). For example, since all the values (col4) of lane1 variable 1 ...
1
vote
1answer
4k views

How can I maintain line breaks in body text with mailx when sending attachments?

I have a script that emails the text of a log file as the body of the email. That log file has some blank lines between lines of text for readability. When I use the following line in the script, ...
1
vote
1answer
64 views

Send multiple files to bash script via Dolphin

I would like to process photos by sending them from Dolphin to bash script with "Open with" feature. But it runs individual instance of the program for each file instead of sending all files to one ...