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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20 views

awk used for duplicate is failing while recreating same file [duplicate]

When i am running command below its just vanishing the complete data from the appirx.txt. Can any one explain the mechanism behind it.It might be basic question awk '!seen[$0]++' appirx.txt > ...
2
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1answer
44 views

How variables inside braces are evaluated

I'm new to shell scripting and I came across these expressions ${var:-val} and ${var-val} ${var:+val} and ${var+val} ${var:=val} and ${var=val} so how are they evaluated and what are the ...
1
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0answers
10 views

find-like tool to search (recursively) in MailDir folders by size, sender, recipient, attachment name regex, etc

I am not looking for a tool like locate, that works by creating an index in the MailDir, or generating other runtime files there; I am searching for real-time, direct search on live MailDirs. The ...
0
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1answer
35 views

Shell prompt displays .f>

I am running SSH through this command: ssh <machine-name> But instead of seeing the machine name in the prompt, I see .f>. Normally the prompt looks something like machinename> Any ...
6
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4answers
260 views

Run command in bash after a certain length of time has elapsed?

If I'm executing a long process, is there any way I can execute some time-based commands? For example, I'm running a really long process which runs for roughly 10 minutes. After 5 minutes, I would ...
3
votes
1answer
15 views

Start new process group in .xinitrc

I have a statusbar (lemonbar) to which I pipe the output of a couple of scripts (time, battery, volume, etc.). These scripts, and the statusbar itself, are all started in a single bash script ...
2
votes
1answer
35 views

Get DISPLAY value by username

I run following commands to get DISPLAY value for a logged in user. $ loginctl list-sessions SESSION UID USER SEAT c2 1000 asif seat0 ...
3
votes
1answer
40 views

Shell syntax for redirecting arguments?

If I want to redirect not the stdio but as arguments the output of a program , should I use xargs? For example, I do ls and I want the filenames to be arguments to the next command rather than an ...
1
vote
1answer
30 views

Move files several directories up for several directories with similar layout

I have a directory with the following layout (the layout in Directory 1 is repeated in every other Directory <num>): Parent directory Directory 1 some directory another ...
1
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3answers
31 views

how to spawn a separate process in the background while running a foreground process

e.g., I want run a python -m HTTPSimpleServer in the background while running a watch in the background python -m HTTPSimpleServer; watch -n (my awesome test command) how can I run both in ...
2
votes
1answer
50 views

on-line tally of unique lines

uniq -c is very useful for counting the number of times the same line appears consecutively $ seq 1 1000 | awk '{ if ($1 > 100 && $1 <= 200) { print "hi" } else {print "bye"} }' | uniq ...
2
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4answers
45 views

Access a file located with find

In many cases after I find a file using the find command I then want to open the file or cat it or maybe print it. How can I operate on the result from find? For example, : find . -name "myfile.txt" ...
2
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1answer
78 views

what is the difference between “./command” and “bash command”

I have simple bash script file, it contains only one line: rvm gemset use --create 2.0.0@PRJ_NAME If I run this script with: ./scriptname.sh I get a well-known error message from RVM RVM is not ...
0
votes
1answer
45 views

How to merge or join more than 2 files? [duplicate]

I have four files; file1: gene_id FPKM TRINITY_DN56960_c4_g1 36.91 TRINITY_DN42427_c0_g1 12.83 TRINITY_DN48728_c0_g1 6.22 TRINITY_DN50706_c0_g2 6604.75 TRINITY_DN51449_c1_g1 8.19 ...
1
vote
2answers
44 views

Use variables in here-string

To feed input to an interactive script, I've been using a here-string: script <<< $'1 2\n3 4\n5 6\nq' This effectively enters 1 2 3 4 5 6 q into the script. But how can I replace one of ...
1
vote
2answers
17 views

Get owner / user of a cronjob

In Linux (Mint / Ubuntu), I can create cronjobs for each user individually. Is there any way, I can find out the name of the user against whome the cronjob is running. I want to get the username of ...
1
vote
2answers
40 views

A quicker way to change owner/group recursively? [duplicate]

Currently, when I want to change owner/group recursively, I do this: find . -type f -exec chown <owner>.<group> {} \; find . -type d -exec chown <owner>.<group> {} \; But ...
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0answers
35 views

How to write the shell script which check if the file is present on the cluster file system?

Suppose we have pscp on Windows, and remote control to Linux cluster through key key.ppk, the user and host is name@cluster.com. How, by using shell script (in cmd file), check if some file is present ...
0
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2answers
40 views

Shell Script to insert lines in between file

Suppose there is one file1.txt where content is written Ramesh Suresh Raman From the below shell script ,I am reading the content name from file1 .txt and preparing the Name=$line in echo ...
3
votes
4answers
117 views

Where should I save color codes for the PS1 command line / terminal? [closed]

This question is about best practices. I know logging in over secure shell or switching users su, and su -l have different effects. Also, in the event you make a typo in the configuration, you still ...
0
votes
0answers
37 views

Send command to open process in Shell file

In bash how can I issue a command to a running process I just started? For example; # Start Bluez gatttool then Connect to bluetooth device gatttool -b $MAC -I connect # send 'connect' to the ...
3
votes
1answer
25 views

.ksh session hangs after being inactive

While remotely connecting to a Linux machine using ssh, my .ksh session hangs after being inactive for sometime. If I try to type or ctrl-z, the prompt does not respond. Is there a way to restore my ...
4
votes
4answers
50 views

Does \ work for escaping functions?

I have a function defined in my .bashrc that I would like to bypass: function func() { // func } export -f func When I run env -i func I can access the func command without the function in the ...
1
vote
1answer
39 views

Shell Font Over SSH

I have a Linux machine (CentOS 7) in which I frequently SSH into from multiple devices. I have installed ZSH and Oh-my-zsh on the remote machine. I would like to install the following theme: ...
1
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2answers
51 views

Help me please to find my misunderstanding about this little piece of shell script

Actually, I have a folder which contains several sub folders with lots of images in each. I am trying to gather all the names of the files in each sub folder in a text file (filesNames.txt) in that ...
0
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1answer
51 views

Validate user response in shell script

My shell script is working fine and the files are copying to the remote directory. However I need to check if my INPUT_STRING is starting with S and also check if the files are present in the ...
1
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3answers
64 views

Where are shell variables stored?

For example, if I make a parameter expansion: $ b=1 $ echo $b 1 Where is b stored internally? I checked and it is not an environment variable because it is not listed by printenv. I'm writing my ...
0
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0answers
16 views

Unable to execute the rest of my shell script after installing Oh My Zsh [closed]

I thought that here it will be better to ask for help with my problem. In a nutshell: I'm creating my custom shell script to simply customise my Mac. To make a short example: 1) I install OMZ using ...
46
votes
5answers
2k views

Why is the wild card character * so different between commands zip and rm?

I put together a script to do some file operations for me. I am using the wild card operator * to apply functions to all files of a type, but there is one thing I don't get. I can unzip all files in a ...
1
vote
1answer
22 views

When a shell executes an external command/program - does that program have file descriptors?

There are alot of documents and discussion around the file descriptors of shells and how those file descriptors can be manipulated for redirection etc. My question is, when a shell command is an ...
3
votes
0answers
54 views

Exploit in bash script parameter possible?

I want to pass an e-mail address from a web form to a bash script. I'm using the following regex: /[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}/ Is this sufficient? Or could one embed an ...
2
votes
2answers
28 views

efficient wait until NAS boots to mount it

Problem: Server boots 3 minutes, Raspberry Pi boots 30 seconds. After a power outage, RPi boots faster and does not mount the NAS disk. This particular RPi needs disk to be able to record to it. ...
2
votes
4answers
54 views

Create text corresponding to multiple variable assignments from a single variable

I have a variable that has a value like this line=dog,/path1,/path2 What I want is to create a variable from the value; i.e dog should be the variable and want to get the below output: ...
2
votes
1answer
30 views

Find differences of ownerships between two home folders?

I have two home folders: /home/masi and /home/masi_backup and I would like to find the differences between files of the two directories. Pseudocode vimdiff <`ls -la /home/masi` <`ls -la ...
1
vote
1answer
57 views

Get the canonical path for a command

I'm writing a script that needs canonical path of certain commands. Since there could be symbolic links pointing to the actual commands, I use readlink -f to get the canonical path. But I'm not ...
0
votes
1answer
24 views

how to echo/print block by block

I just started using tmux and butterfly and I need to scroll one panel. I tried Ctrl + b + ↑ but it scrolled the whole terminal instead of one panel. Is there any command line to display my ...
1
vote
1answer
37 views

xkill Used On Desktop

Mouse accidentally clicked on Desktop while active with an xkill terminal command. Which makes it completely without use. Have used nemo command which resets everything as long as terminal remains ...
2
votes
2answers
59 views

Split words from `read` and store to array?

How can I take input from read, split the words up by spaces, and then put those words into an array? What I want is: $ read sentence this is a sentence $ echo $sentence[1] this $ echo $sentence[2] ...
0
votes
2answers
48 views

cut -c won't work on my .sh file [closed]

I have tried the following commands cut -c-11 ifshell.sh cat ifshell.sh | cut -c-11 ifshell.sh cat ifshell.sh | awk '{print $1} | cut -c-11 ifshell.sh But every time I get the full contents of ...
1
vote
4answers
56 views

How to gather the name of the files in each subdirectory into a text file in that subdirectory?

I wanted to save the names of all files in each sub directory into a text file in that sub directory, so I wrote this script: #!/bin/bash for X in "$PWD" * do if [ -d "$X" ]; then ...
0
votes
1answer
19 views

Why does the jobs command not work in shell script?

If I run jobs -l on command prompt it shows me the status of running jobs but if I run below file ./tmp.sh #! /bin/bash jobs -l It shows empty output. Why is that and how can I obtain information ...
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votes
1answer
15 views

can a service like isup.me be duplicated on the system for self? [closed]

The Internet or Web as I understand it runs on variety of servers. The browser is the client which gives a URI or URL which tries to go through varied ways to connect to the web-page and render the ...
14
votes
2answers
794 views

Colored output?

When I execute a command from a terminal that prints coloured output (such as ls or gcc), the coloured output is printed. From my understanding, the process is actually outputting ANSI escape codes, ...
0
votes
3answers
55 views

Efficiently compare If variable exists and is not equal

I have a problem with the sh script syntax. I wrote a script for my Asus router. The script works perfectly. But I have this line: if [[ "$OldIP" && "$StartIP" != "$OldIP" ]]; then echo OK; ...
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0answers
13 views

MongoDB Shell Commands

i want Run shell command(s) from MongoDB , i connect to My MongoDB With MongoVUE now i want execute shell Command like ls -l can i do it From MongoVUE ?
10
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14answers
2k views

'ls -1' : how to list filenames without extension

ls -1 lists my elements like so: foo.png bar.png foobar.png ... I want it listed without the .png like so: foo bar foobar ... (the dir only contains .png files) Can somebody tell me how to use ...
1
vote
1answer
24 views

tmux: how to bind a key to launch shell command?

I use tmux to develop, with two panes: one to edit the code, and one to compile it. I need to switch pane very often to launch the compile command (say "mvn install"). How can I bind a key (say ...
1
vote
1answer
44 views

Extracting files to current directory

I want to find and tar/archive all my scripts ending .sh so I wrote something like that: touch ~/archive.tar; find ~ -type f -name '*.sh' -exec rvf ~/archive.tar {} \; The problem is that after I ...
0
votes
1answer
64 views

How to pull database file from physically connected android device

I am trying to copy WeChat database file called EnMicroMsg.db so I can view it in SQLite browser. With my Nexus 7 tablet rooted and physically connected, the usb debugging checked I ran the following ...
0
votes
1answer
33 views

Is using env and export the same thing?

I'm wondering whether this (From https://www.digitalocean.com/community/tutorials/how-to-read-and-set-environmental-and-shell-variables-on-a-linux-vps): env VAR1="blahblah" command_to_run ...