The shell is unix's command-line interface. You can type commands in a shell interactively, or write scripts to automate tasks. Use this tag for questions applying to /bin/sh and most compatible shells (ash, bash, ksh, zsh, …).

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1k views

list files and store it in variables

im new with shell programming. my goal is to give the user a selection which file should be run. i catch all available scripts in one var with: var=$(find script*) so far so good.. this is the ...
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2answers
71 views

How to get text at start up of terminal

How to get text at start up of terminal as shown in this image.It should show whenever i open terminal.
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1answer
987 views

How do I use colors in the MOTD?

I edited the default /etc/update-motd.d/00-header, adding some color to make it easier to read: printf "Welcome to \e[1;34m%s\e[0m \e[2m(%s %s %s)\e[0m\n" "$DISTRIB_DESCRIPTION" "$(uname -o)" ...
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1answer
314 views

How to simulate user interaction when running another script

I am new to shell scripting. When I want to run a bunch of Linux commands I do fine, but how do I give user input when another script is called and asks for input while it runs. Here is the situation ...
6
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2answers
461 views

if statement in .bashrc not working correctly

I set up .bashrc to show a long prompt if the terminal is at least 80 characters wide. Otherwise it shows a degraded, smaller prompt. I use an if statement to achieve this: dp_smaller_than=80 if [ ...
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4answers
1k views

How to initialize an array using awk and bash?

I am trying to store values of the first line of a text file into an array. Here is what I have so far: arr_values=() awk ' NR==1 { for (i=0; i<=NF; i++) ...
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3answers
366 views

Is there any harm in using variables that aren't set?

Say I have the following code: # Check if the color prompt is enabled and supported on this system if [ -n "$force_color_prompt" ] && [ -x /usr/bin/tput ] && tput setaf 1 ...
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2answers
1k views

Cannot sum numbers received from stdin using bc

I'm trying to calculate the average entropy of files contained in a folder using: { echo '('; find . -type f -exec entropy {} \; | grep -Eo '[0-9.]+$' | sed -r 's/$/+/g'; echo '0)/'; find . -type f | ...
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3answers
47 views

How to run executable program with filter

I want to run a shell script. This script have a long name. So I want to use filter for file. ex: ls | grep myfile | ./ Is it possible to execute a file with filter.
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2answers
76 views

Start several fish shells in different directories?

In order to be able to launch my work environment with a single command, I want to start several urxvt windows running fish shell in different folders. However, I found no obvious way of having fish ...
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1answer
138 views

Kill all queued jobs

I need to kill all the queued and running jobs on my ID. I have tried at -l | awk '{print $1}'| at -r {} But I keep getting {} does not exist Which leads me to believe that I am parsing ...
5
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1answer
119 views

Why does `bash -c somecommand` sometimes not leave a bash process?

On an Ubuntu 12.04, with GNU bash, version 4.2.25(1)-release (x86_64-pc-linux-gnu), I tried the following command: $ bash -c 'pstree -s $$' init───sshd───sshd───sshd───bash───pstree $ bash -c 'pstree ...
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3answers
79 views

Can we configure different shells for different users on a single Linux/Unix distribution?

Well, this is not something that I want to do but I ask this question to know more about Shell configuration in Unix/Linux systems. So, the situation that I want an answer to is the following -: As ...
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3answers
264 views

Which amongst the given option is TRUE about login shell?

Which amongst the given option is TRUE about the login shell? The login shell varies every time the user logs in. The kernel decides on the availability of the shell during login. The login shell ...
0
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1answer
415 views

Bash Script : Passing a variable to a bash script that contains quotes, single quotes. etc [closed]

lets assume this is the string: 'a',"b" it contains both single and double quotes. how would you pass this to a bash script as a single string ? this is the bash script: #!/bin/bash echo $1 ...
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2answers
351 views

“cat” command: how to automatically escape everything that might be a violation?

If you copy the contents of httpd.conf and then paste it into a cat command.. such as this one.. #!/bin/bash cat > /test << EOF pasted here.. EOF you run into this error: -bash: ...
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2answers
4k views

How do I sort using the grep and sort commands?

I would like to create a sorted list of all TCP services found in the file /etc/services, pipe the output of the command grep tcp /etc/services into the command sort, then redirect the output of this ...
4
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3answers
620 views

Can I chain pgrep with kill?

I have noticed that | is used to send results of first command to the another. I would like to kill all processes that match a name. This is what pgrep normally does: $ pgrep name 5089 5105 And ...
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5answers
68 views

grep for text that may or may not be present

Lets say I have a file batman; robin; superman; password = ""; wonderwoman green lantern if I want to check if there is a password present, i.e there is something entered in the "" . here is an ...
1
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1answer
79 views

Assign diff -y column names

I have two files and a shell script. File 1: Batman Superman John Snow Jack Sparrow Rob Stark File 2: Batman Ironman Superman Spiderman John Snow Arya Stark Jack Sparrow Rob Stark The hound ...
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5answers
115 views

Resources to learn shell scripting [closed]

I have been using GNU/Linux for sometime now (Ubuntu and Fedora) and now I am trying to learn shell scripting from scratch. I would really appreciate if someone can guide me on choosing right ...
0
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2answers
1k views

Running system bash command in PHP script - syntax error: unexpected T_LNUMBER

If anyone can shed some light on my issue that'd be great. Please don't down-vote me; I'm new to the language and the OS itself and I'm trying my best to research before asking questions, so any ...
1
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1answer
64 views

Awk that I am stuck on

I have a project I am working on for work. The script I am building initially takes two arguments: one is an unique Identifier and the other is for a log file (both strings). Now I have the first part ...
3
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4answers
808 views

How to cut everthing until a specific word / after a find in a script

Hello I try to get the output of files from today wich contains ERROR. I use this to find the files I want: find /home/user/logfilesError/ -maxdepth 1 -type f -name "gandalf_*"\ -daystart -mtime ...
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3answers
121 views

Finding and replacing text inside awk block

I want to find and replace a value inside awk block. Here is a sample input file to my script P1 10,9:11/18013013582 ,10:1 ,167:0 ,487:5/E.164 11,9:15/310410532169026 ,10:60 ,167:0 ,487:4/IMSI ...
2
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1answer
532 views

bottomless tee?

I was just playing around in the terminal and I did this: printf 'some string\n' | { tee /dev/fd/3 | { : && sed 's/some/string/' } } 3>&0 I was really surprised when ...
9
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3answers
3k views

Local, timestamped logging of all ssh commands?

How can I keep a local, timestamped record of all remote commands I use in ssh (command-line openssh client started through bash)? Requirements: Essential: 100% client-side without relying on ...
5
votes
3answers
10k views

Difference between ls -l and ll?

I'm relatively new to programming as a whole and some tutorials have been telling me to use ls -l to look at files in a directory and others have been saying ll. I know that ls is a short list, but ...
4
votes
1answer
796 views

Rename files with spaces in a BusyBox shell

I'm trying to rename some files on my Synology Diskstation via SSH. The available shell is the BusyBox built-in shell: BusyBox v1.16.1 (2013-04-16 20:13:10 CST) built-in shell (ash) The move ...
9
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2answers
5k views

Array in unix Bourne Shell

I am trying to implement array in Bourne shell (/bin/sh). I found that way to initialize array elements is: arr=(1 2 3) But it is encountering an error: syntax error at line 8: `arr=' unexpected ...
0
votes
1answer
181 views

How do I cat a command file?

I have the output of the crontab -l stored in a file (crontab_file) with no extension. But whenever I try to cat it, I get errors saying command not found for multiple line of the file. Here is the ...
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2answers
752 views

Gzip large amount of symlinked files

I have a folder containing a large amount of symlinked files. These files are each on the order of 10-11GB (fastq files to be specific). They come from a variety of source folders, but I made sure ...
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5answers
104 views

Is there a way to find out the number of lines from a command output?

I am trying to compare command outputs between two servers. I want to find out the number of lines from the output of commands such as ls -l. Is there a way to do so? So far I have not found anything. ...
2
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1answer
282 views

History in the Almquist shell in the NetBSD

In NetBSD /bin/sh is a modified version of the Almquist shell. With the command fc -l it is possible to view the last 16 commands typed in the prompt in the current session and not the older ones. ...
2
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1answer
102 views

stdout is empty

When a run the command: cellprofiler --get-batch-commands "/users/pmrotem/CellProfiler/example_project/output/Batch_data5_8.h5" in the shell, I get an output: CellProfiler -c -r -b -p ...
4
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3answers
146 views

zsh's “echo SomeText >> **/filename” in other shells

I need to fill all files with a specific filename (recursively) with a text. In zsh this can be done with echo SomeText > **/TheFileName I search generic solutions for sh-compatible and/or tcsh ...
3
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4answers
190 views

Protected environment variables?

Are there names of environment variables that cannot be overwritten by the user/a call to setenv? As I understand from POSIX1.2008, any process may edit the environment block, but must avoid ...
1
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1answer
113 views

Getting the parent path from a script

I have a bash script foocaller, which calls a ruby script foo: foocaller /path/to/foo Within foo, I want to get the path of foocaller. Following this suggestion, I put the following code to do ...
29
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3answers
2k views

What does `{ { (exit 1); exit 1; }; }` mean?

I quoted the next code snippet from config.status generated by configure. if test ! -f "$as_myself"; then { { echo "$as_me:$LINENO: error: cannot find myself; rerun with an absolute path" >&5 ...
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1answer
38 views

Make an alias that does an alias command

I have to make an alias that will do the alias command. It has to "replace" the alias command and the user has to feel no difference..
4
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2answers
306 views

Execution order with multiple commands

I'm relatively new to Linux and I'm working on a CronTab for scheduled backups. I figured out how to do multiple sequential jobs with ; and &&, but I'm unsure how the dependency affects the ...
3
votes
1answer
281 views

How to move a window to a different workspace using its ID, in bash?

Currently I have successfully used wmctrl -r :SELECT: -t 2 but something like wmctrl -r -i 0x03e00003 -t 2 does not work. How should I write the command in order to select the window to be moved ...
5
votes
1answer
145 views

What are the difference between those four commands (fifo, process substitution, redirection…)

My goal is to create a simple echo server using nc and a single fifo. I'm not looking for the best way to do it, I'm merely trying to understand the semantics of the following commands (when does fork ...
1
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1answer
58 views

Matching two files, line by line? [closed]

I have two files consisting of numbers. Now, I want to match the line of first file to all the line of second file and increasing the counter if the match is found. How to write the bash script for ...
6
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5answers
804 views

Serialize shell variable in bash or zsh

Is there any way to serialize a shell variable? Suppose I have a variable $VAR, and I want to be able to save it to a file or whatever, and then read it back later to get the same value back? Is ...
2
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1answer
262 views

Mysql synonym drop and create

I am running into the issue that, when the script is run, the MySql section of it isn't working or is droping the synonym. Is there something else i need to put into the command to have it log into ...
2
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4answers
1k views

Get the latest directory (not the latest file)

My folder parent has the following content: A.Folder B.Folder C.File It has both folders and files inside. B.Folder is newer. Now I just want to get B.Folder, how could I achieve this? I tried ...
4
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3answers
730 views

Can't open shell after changing default shell

I changed my default shell to zsh from bash in Ubuntu. I used the steps explained in http://github.com/sorin-ionescu/prezto and ran chsh -s zsh. After this, I couldn't able to log in to any shell as ...
2
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1answer
390 views

Why is my tar in a script behaving different than using tar manually

I'm writing a backup script for my email and cloud service. For simplicity, I only posted the mail-backup part here. Basically, I have a Host-Machine with some Virtual Boxes running in it. These ...
7
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6answers
14k views

How to use the sed command to only show the first column and last column in a text file

I need some help to figure out how to use the sed command to only show the first column and last column in a text file. Here is what I have so far for column 1: cat logfile | sed 's/\|/ /'|awk ...