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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How to pass multiple commands via pssh and multiple xterms

I'm attempting to open multiple xterms and run a command as an SAP user via sudo using pssh. So far, I'm able to run PSSH to a file of servers with no check for keys, open every xterm in the servers ...
5
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1answer
19 views

Getting the process-id out of command launched with “su -c”

I am running a java program inside a shell and writing the process-id to a text file. So when I do this: nohup java app.Main > /dev/null 2>&1 & echo $! > /var/run/app.pid It works. ...
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4answers
47 views

Renaming multiple files with rename

I need help renaming files in batch--the other questions I browsed don't exactly address my problem. The names of my files are generated non-deterministically, so I can't predict what they will be ...
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1answer
22 views

How to find the cpu and memory usage of child processes

Supervisord is running on centos server. If I do ps -e -o %mem,%cpu,cmd | grep supervisord | awk '{memory+=$1;cpu+=$2} END {print memory,cpu}' I get 0 0 just because supervisord is just an ...
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4answers
210 views

Convert key=value blocks to CSV

I am trying to transpose a content of a file into another. I am new to shell scripting any help would be really appreciated Input file Test.txt: HLRSN = 3 IMSI = 404212109727229 KIVALUE = ...
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2answers
43 views

Create an absolute symbolic link to the current directory

I am now under a directory with very long path. For future visiting it quicker, I would like to create a link to it. I tried ln -s . ~/mylink ~/mylink actually links to ~. So can I expand ~ into ...
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22 views

Detach a process from Sh (not Bash) or “disown” for Sh (not Bash)

Consider a shell script executed by Sh, not Bash (and I can't change it, and can't use a shebang, it's ignored). The & operator works, but disown $! does not and makes Sh complains “disown: not ...
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3answers
286 views

What is the difference of -a and -e in bash's conditional expressions?

From man bash: CONDITIONAL EXPRESSIONS [...] -a file True if file exists. [...] -e file True if file exists. So what is the difference between [ -a $FILE ...
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2answers
27 views

Select a range of files after sorting them

One thing I notice slower for me if I switch from using a GUI file manager to CLI is: In a GUI file manager, I can quickly select a subset of files under a dir by, first sorting them according to ...
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18 views

Cortex Application [on hold]

Cortex Acquirer & Issuer is a software application supporting a wide range of card payments functionality including Debit, Credit and Prepaid card issuing, card management and authorisation, ...
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1answer
34 views

Who does the linewrap and how to deactivate?

If I connect to a linux device via serial adapter (no matter if pyserial, screen or minicom), and no matter how I change settings like stty when I enter a long command it gets line wrapped ...
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1answer
125 views

How does execution of !find command work?

The !find command lets the user perform the previously executed find, with all its parameters. How does it work internally, where exactly has this behaviour been programmed?
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2answers
27 views

Variable assignment outside of case statement

In many languages it is possible to assign the result of a case/switch statement to a variable, rather than repeating the variable assignment many times within the case statement. Is it possible to ...
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7answers
1k views

How do I repeat the last command without using the arrow keys?

I know I can use Up to iterate through previous commands. Running the last command simply involves Up + Enter. However, I was thinking of buying the Happy Hacking Keyboard as I spend a lot of time in ...
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2answers
25 views

Read Multiple Entries from an Input File

I wrote a program in Fortran that asks me for latitude and longitude and the name of the output file every time I run it. It works great. What I have been meaning to do is run this program for the ...
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1answer
27 views

What is the term “Usage”?

I am seeing this a lot in the scripts. Is "usage" a command in unix ? I tried googling it but got ambiguous results. Here is an example : ${1?"Usage: $0 ARGUMENT"}
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1answer
34 views

Compare two strings in a shell script [duplicate]

My script needs two arguments. I want to hide the error message if someone calls the script with script.sh --help so I tired this: if [ $# -ne 2 ] ; then if [ "$1" -ne "--help" ]; then echo ...
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1answer
36 views

How to evaluate a variable length in shell script?

I want to write a shell script, in which it will call different command according to the variable length. But I didn't figure it out yet. My unwork script is here: for i in n5 n25 if ${#i} == 2; ...
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3answers
143 views

What is $() in a command?

What is $() in Linux Shell Commands? For example: chmod 777 $(pwd)
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1answer
20 views

Change the PS1 prompt in a subshell sh called from parent bash

When I am running an interactive bash session, I sometimes experiment with sh. I call sh directly from this bash session. My question is, how can I change the PS1 prompt of this subshell? I would ...
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0answers
45 views

How do I execute in background / return early?

For reference, I'm using phpseclib to control a remote SSH server using the 'root' account. I have to start/stop a java process which is ran in the background. Stopping works fine with killall java ...
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2answers
29 views

change boot order

I have 2 partitions sda1 XP and sda2 CENTOS. I have reinstalled grub on /dev/sda but on rebooting, I experienced: error : 22 no such parition for Centos; while Windows boots charmingly on the other. ...
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1answer
41 views

Answer password prompt programmatically via shell script

I would like to programmatically answer a password prompt using only shell script when prompted. Is it possible to automate this task in this way? I want to avoid other tools entirely - so no expect ...
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1answer
28 views

Recover files after moving directory names?

During the course of some testing, I ran the bast script for file in *; do mv -v "$file" "$file#_*" done or something along those lines. The plan was to remove a prefix from directory names ...
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2answers
49 views

If statement question

I am scratching my head to understand this script and can certainly use some expert advice. getopt_simple() { echo "getopt_simple()" echo "Parameters are '$*'" until [ -z "$1" ] do ...
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3answers
369 views

how to get the basename of complicated files [duplicate]

Here is an example of file path: /isf/GCM/VPfig/Aas/AR/ClCo el Doma Republic/VMN CRTro.txt What I want to get is the file basename: VMN CRTro.txt So I try the following: echo ...
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2answers
67 views

Ping multiple hosts and execute command

I'm very new in bash scripting and unix so I will need some help on this.I have 7-10 hosts which I want to ping from one of the servers via cronjobs. What I want is when host is up to execute command ...
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11 views

Chrome OS: Crosh Window and Hostname

I have a couple of questions regarding Chrome OS: By default Ctrl+Alt+T opens a crosh window within the Chrome browser. I have the Crosh Window extension, which I would like Ctrl+Alt+T bound to - ...
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6answers
371 views

How can I test if a variable is empty or contains only spaces?

The following bash syntax verifies if param isn't empty: [[ ! -z $param ]] For example: param="" [[ ! -z $param ]] && echo "I am not zero" No output and its fine. But when param ...
8
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3answers
204 views

Going into a directory linked by a link

When I cd a link, my current path is prefixed with the link's path, rather than the path of the directory the link links to. E.g. ~/dirlinks/maths$ ls -l logic lrwxrwxrwx 1 tim tim 71 Jul 27 10:24 ...
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1answer
43 views

regenerate xorg.conf with current settings

Many people have talked about this issue but I've not found a satisfactory answer. I'm on a debian jessie. Currently I have tried nvidia-driver as the driver but it caused the system to crash; so I ...
2
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1answer
45 views

Forward SIGTERM to child in Bash

I have a Bash script, which looks similar to this: #!/bin/bash echo "Doing some initial work...."; /bin/start/main/server --nodaemon Now if the bash shell running the script receives a SIGTERM ...
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3answers
53 views

grep substring between quotes

Let's say I have a string like this: title="2010-09-11 11:22:45Z" How can I grep the date itself and disregard the quotes/title/Z? The file can contain more strings like: randomstring ...
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2answers
770 views

Does ~ always equal $HOME

I know this has probably been asked before, but I couldn't find it with Google. Given Linux Kernel No configurations that change $HOME bash Will ~ == $HOME be true?
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1answer
111 views

Proper way to distribute shell scripts

What is the most proper way to distribute shell scripts, if behaviours of shells can be modified by set and thus are unpredictable? For example, rm *.txt wouldn't be executed as expected on the ...
4
votes
4answers
112 views

Check if content of file has length X and contains only specific characters

Let's say, I have files that contain only one docker id: myid.id: 28fe2baadbe8da32ed0b99c69b11c01b2d141bc5b732b81e0960086de52fc891 I want to check if the content of my.id is exactly 64 characters ...
2
votes
1answer
37 views

Arrow key/Enter menu

I need help finding out how to possibly create a menu in a shell script that will display 3 options that a user will use the arrows keys to move the highlight cursor and press enter to select one. If ...
5
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1answer
422 views

What does su - `whoami` command do?

I am running a script in my project and I see this command su - `whoami` I am having a few basic questions: What does this command do ? What is the significance of `` quotes outside the whoami ...
4
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2answers
123 views

sed to search for multiple words and remove those lines

I have a master file with more than 50000 lines and my requirement is to remove around 20000 lines from actual file, for this I used grep -vE command which is showing an error as too many arguments. ...
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3answers
54 views

List all the html tags in a file

I want to know if there is a way to list all the html tags in a file. Lets say I have a file file.html <html> <head> <title>Test</title> </head> <body> This is a ...
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2answers
52 views

Decoding “prog > file 2>&1”

I am having some difficulty understanding the construct prog > file 2>&1. I have read that it means "Send stdout and stderr to file". But my question is how? I understand that prog > ...
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0answers
15 views

Mirrored Linux Commands [duplicate]

I've encountered two incidents where commands (or logic flow) is given forward and backwards In bash scripts: if ... fi (use to closed an if-statement) and in GNU/Linux command line: cat; tac (cat ...
5
votes
3answers
182 views

How to remove dot and space from beginning of filenames

I'm trying to change jpg files named with a dot and a space at the beginning and with a missing dot before the end (like this . Startjpg to Start.jpg The dot makes the files hidden from sed and ls ...
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1answer
79 views

What Causes Maintenance Shell Segmentation Fault?

I'm running Ubuntu 14.04 Trusty Tahr in a Microsoft Hyper-V virtual machine on Windows Server 2012 R2. I've stopped the VM, replaced an EXT4-formatted virtual disk volume (/dev/sdb) with a new ...
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2answers
30 views

I seem to be “losing” this prompt. What is happening?

I ssh into an ubuntu 12.04 cloud server and start a web server like this (w/ bash): $ nohup python tserver.py & [2] 2122 $ nohup: ignoring input and appending output to `nohup.out' After I run ...
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3answers
338 views

Replace multiple spaces with one using 'tr' only

I have a file, f1.txt: ID Name 1 a 2 b 3 g 6 f The number of spaces is not fixed. What is the best way to replace all the white spaces with one space using only tr? ...
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2answers
66 views

How can I pipe stdout to another program?

I'm trying to setup a linter for my code and I only want to lint the coffeescript files that have changed in the current branch. So, I generate the list of files using git: git diff --name-only ...
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2answers
59 views

How to change my script to replace and add new variable in a configuration?

Well this is my script. It is to configure my systems sysctl.conf. infile = open('sysctl.conf') outfile = open('sysctl.conf.new', 'w') replacements = {'Net.ipv4.icmp_echo_ignore_all' :'1', ...
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votes
1answer
40 views

Faillog - unsuccessful login count in Motd

I wish to include a count of failed login attempts whenever a user logs in. I've created: /usr/local/bin/dynmotd which contains #!/bin/bash FAILLOG=`faillog -u` echo -e " $FAILLOG " and ...
3
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2answers
27 views

How to build space separated, escaped full paths of files recursively matching glob?

I have a program which requires paths to files as arguments, which cannot be quoted and must not depend on working dir. Can this be done without chaining multiple xargs, tr, find, readlinks? Example ...