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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6
votes
1answer
14k views

Linux - Sending a command to a screen through a shell script? [duplicate]

I'm trying to figure out how to make a script that will be able to send commands to a screen that will execute within whatever the screen is doing. Is this possible, and if so, how is it done? I've ...
3
votes
1answer
125 views

Common flag designations and standards for shell scripts and functions

I have been adjusting to using GETOPT and GETOPTS in my shell scripts and custom functions to enable me to use the functions that I create more flexibly. After using a number of UNIX functions I have ...
0
votes
1answer
130 views

What distribution do you suggest for daily use? [closed]

I use my computer everyday for various reasons: programming in c++, android(java), java(in general) listening to music(spotify), watching movies browsing internet, watching youtube clips writing ...
1
vote
1answer
186 views

Linux - How to open a console and display command results on startup?

I have a Linux server with a screen always displaying the end of a very usefull file. How could I automatically enter a shell and display the end of this file when the server starts? I'd like to do ...
13
votes
7answers
23k views

How to restart the Python script automatically if it is killed or dies

I am running my Python script in the background in my Ubuntu machine (12.04) like this - nohup python testing.py > test.out & Now, it might be possible that at some stage my above Python ...
-2
votes
1answer
104 views

How to modify the shell prompt? [duplicate]

I would like to learn how to make my shell look like this: [user@host ~/Folder] $ instead of (the default): [user@host ~/Folder]$. Also, I'd like to have color on user@host and Folder. How can ...
2
votes
3answers
143 views

Code duplication in a shell script

My bash script (lets call it myscript) takes input either from stdin (pipe), or form a regular file (if filename was provided as an argument) a) someprog | myscript or b) myscript file.txt ...
4
votes
3answers
532 views

processing command output line by line, without mixing standard input

So, I have a problem very similar to Bash: How to read one line at a time from output of a command?, I am doing: while read path; do mplayer $path; done < <(find-me-random-mp3s) or ...
2
votes
1answer
1k views

How do I change login shell to nologin for an LDAP user RHEL 6?

yum install ypchsh and yum install ldapmodify both don't find a package. I only want to change the shell for certain ldap users on this one server. Someone please help, I can't seem to figure this ...
1
vote
2answers
215 views

Merging two different files with conditions

I have two different files as shown below. Content of a.txt: HDR|1|||||||||| DTL|@||||||||||| TLR||||||||||||| HDR|1|||||||||||| ...
2
votes
1answer
599 views

How can I use “emulate sh” in zsh to work with “. myscript.sh”?

I've been using emulate sh -c ". $HOME/myscript.sh" and it's working so far. However, if I'm at ~ and try to do emulate sh -c ". myscript.sh", I get .: no such file or directory: myscript.sh.. Why?
12
votes
2answers
1k views

Shell filename pattern that expands to dot files but not to `..`?

Recently I had a little mishap caused by a shell pattern that expanded in an unexpected way. I wanted to change the owner of a bunch of dot files in the /root directory, so I did chown -R root .* ...
5
votes
5answers
1k views

What are the special characters to print from a script to move the cursor?

I found that by printing \r from a script the cursor moves to the beginning of the line. What character will move the cursor up one line? Where is a list of these special characters? EDIT: Working ...
4
votes
1answer
286 views

CPU is free, yet bash script not utilizing all CPU resources

I ran a simple script to generate a large (10000000 lines) csv file with 6 fields in which some fields changed in each line/row, using a while loop. The machine had all (32) CPUs free, lot of RAM (~31 ...
6
votes
4answers
11k views

Ctrl-C with two simultaneous commands in bash

I want to run two commands simultaneously in bash on a Linux machine. Therefore in my ./execute.sh bash script I put: command 1 & command 2 echo "done" However when I want to stop the bash ...
2
votes
2answers
243 views

Error message on terminal despite using 2> symbol

Why does this command show error message despite using 2> symbol? cat < foo 2>bar bash : cannot open foo : No such file or directory
4
votes
6answers
41k views

Extract date from a variable in a different format

Let me explain you the problem $ date +%c -d "$d" Tue 31 Dec 2013 01:13:06 PM CET $ date +'Today is %F' -d "$d" Today is 2013-12-31 This solution corresponds to current date. But I have one ...
0
votes
0answers
19 views

UNIX: How to extract date from a variable storing a UNIX DATE [duplicate]

I am facing following issue: Input: F=`date +%Y%m%d` echo $F Output: F=20131231 But when trying this(File Name:A.sh): C=`date` G=`$C +%Y%m%d` echo $C echo $G Output: A.sh[6]: Tue: not ...
2
votes
2answers
2k views

Differing outputs of the commands “ls .*” and “ls *.”

The command ls .* when run gives as output the following : All the files in the current directory starting with a . (hidden files) All the files in the hidden directories present in the ...
3
votes
3answers
3k views

How to delete 2 months back files in unix

Say I have below log files, AA_XX_20130719185428.log exec_xxx_cpb_20130712182453.log 13122013121327_AR_INC_DOBC_1.dprf.log 24122013_masterscript.LOG Date part contains both date and time. I want ...
0
votes
5answers
8k views

how to use & for sudo

I know if I put & at the end of application at the terminal, it will run in the background and terminal still can receive commands, for example: howchen@host:~ -> cutecom& [1] 17269 ...
3
votes
1answer
780 views

How to cd into a directory with the name “-”? [duplicate]

I tried to cd into a directory named - that I created for experimenting. I could not from Bash. How do I cd into it? With Nautilus on Ubuntu 13.10 I could easily do this, and even create files inside ...
11
votes
1answer
662 views

Clear old prompt lines in bash to save scroll space

My terminal theme used to be like this, But I thought the prompt wasted so much space. And later I got an idea that I could clean the prompt every time I ran a command. I was using bash, one of ...
5
votes
2answers
2k views

Pass multiple commands to flock

flock -x -w 5 ~/counter.txt 'COUNTER=$(cat ~/counter.txt); echo $((COUNTER + 1)) > ~/counter.txt' How would I pass multiple comands to flock as in the example above? As far as I understand, ...
6
votes
2answers
4k views

Obtain exclusive read/write lock on a file for atomic updates

I want to have a file that is used as a counter. User A will write and increment this number, while User B requests to read the file. Is it possible that User A can lock this file so no one can read ...
1
vote
2answers
612 views

How to loop through xargs where each script uses a common env variable

Is it possible to initiate 10 of the same shell scripts which also initiate more copies, and have them all use the same env variable? For example: script.sh: #!/bin/bash export ...
1
vote
1answer
548 views

Using sed output in another script or command

How can I use the output of sed in another script? For example (this doesn't work): sed -n "$COUNTER",1p /domains.csv | wget or sed -n "$COUNTER",1p /domains.csv > /myScript.sh As far as I ...
1
vote
1answer
336 views

Autocompletion and coloring not working, when using ssh in emacs shell

I'm connecting to remote server using emacs shell. Emacs shell displays directory listings with proper coloring and auto completion when working with local machine. But when I use ssh the ...
0
votes
0answers
652 views

Override LDAP login shell for a specific user in RHEL

How in RHEL do I specify /sbin/nologin shell to limit a user to SFTP access only when their shell is determined by their LDAP profile? chsh only works with passwd file users I believe.
1
vote
1answer
166 views

Crontab Triple Redirect

I have a very basic understanding of redirects, but I have come across a cronjob with redirects which I do not understand. 00 19 * * 1-5 /apps/app/scripts/doit.sh a np cron > ...
1
vote
2answers
1k views

How can I make awk on Busybox treat the entire input with NULL character in between as a single record?

I wrote a base64 encode script for my Busybox system. #!/bin/sh base64encode() { /usr/bin/awk -- ' function asc(char,l_found) { l_found=0; for (i=0;i<=255;i++){ if ...
1
vote
3answers
435 views

linux + awk + file manipulation

I have the following file more file.txt 1 2 3 4 4 2 23 4 5 23 2 3 END_OF_LINE 1 3 7 4 2 23 4 6 7 4 2 1 5 How to print only the fields 4 and 5 and 6 until the line END_OF_LINE , and from ...
25
votes
3answers
10k views

How do you process an entire command as sudo that involves redirecting or piping?

I am trying to follow what I assume is best practises of using sudo instead of root account. I am running a simple concat file operation such as: sudo echo 'clock_hctosys="YES"' >> ...
11
votes
3answers
16k views

How to add a function to .bash_profile/.profile/bashrc in shell?

I have a function which converts epoch time to date. Here is the definition date1(){ date -d @$1 } I'd like to be able to write: $ date1 xxxyyy Where xxxyyy is the parameter I pass into my ...
2
votes
4answers
5k views

How to check the process along with its arguments in process list?

I have written a script where i need to pass several arguments with the same script, the script is being executed after a certain time using cron. In order to make sure that there are no multiple ...
-4
votes
2answers
125 views

z in bash script returns zero [closed]

#[ -z "" ] #echo $? returns 0 #[ -a "" ] #echo $? returns 1 except z all other alphabets throw 1 What might be the reason?
0
votes
1answer
651 views

How to write conditional if statement in bash shell script?

I have a below shell script which will get the latest folder from my current directory in machineB and machineC. So I came up with the below command which will find me the latest folder inside - ...
2
votes
2answers
328 views

How to cd into a directory as part of shell script and do a word count of files?

I am trying to get the latest folder inside my directory in machineB and machineC. So I came up with the below command which will find me the latest folder inside - `/bat/data/snapshot` And that ...
1
vote
2answers
74 views

Running a program to output in Dutch

I'm running KDE Arch linux and trying to update my system using pacman and have it output in Dutch. I've tried the following sudo LANG=nl_NL.UTF-8 pacman -Syy sudo KDE_LANG=nl_NL.UTF-8 pacman -Syy ...
1
vote
3answers
224 views

How do I iterate the list and copy the files from machineB and machineC efficiently?

I need to scp the files from machineB and machineC to machineA. I am running my below shell script from machineA. I have setup the ssh keys properly. If the files are not there in machineB, then it ...
0
votes
2answers
247 views

zsh: What does the command “time + number” do in zsh

When I type time + number in zsh: # atupal at local in /tmp/atupal/setup/bin [10:01:49] $ time 1 /tmp/atupal/setup/bin/lib/python2.7 # atupal at local in /tmp/atupal/setup/bin/lib/python2.7 ...
3
votes
3answers
145 views

capture output from command without interference

How can I test whether a command's output is an empty string without interfering with said output? Example: command | ??? if [ $? = 0 ] && [ -n "$output_from_command"]; then ... I'd ...
2
votes
3answers
1k views

awk print ' char

I want to print: cat file.log | awk '{print nir's $1}' output should be: nir's aaa nir's bbb nir's abc nir's dbc The problem is with the ' in nir's. I also tried: cat file.log | awk '{print ...
2
votes
3answers
7k views

Copy files from a list to a folder

I have a text file abc.txt and its contents are: /lag/cnn/org/one.txt /lag/cnn/org/two.txt /lag/cnn/org/three.txt If I use: $ tar -cvf allfiles.tar -T abc.txt I'm getting the tar of ...
9
votes
2answers
9k views

Is there any way to use xargs across a pipe?

I'm trying to automatically convert flac files moved to a folder into mp3 in another folder. My current line of code is this: inotifywait -m -r -q -e moved_to --format "'%w%f'" ~/test | xargs -I x ...
2
votes
2answers
354 views

Pipeline with grep and find prints numbers infront of result

Am using the following "find" command to extract some files, find /lag/cnnf/ -maxdepth 3 -newer ./start ! -newer ./end | grep -nri abc | egrep '([^0-9]45[^0-9])' | grep -nri "db.tar.gz" >> ...
2
votes
1answer
726 views

Command not found in zsh [duplicate]

In bash, whenever I try to run a command which is not installed, I get a message which tells that the package is not installed and how to install it. This functionality is provided by installing the ...
9
votes
3answers
2k views

Why does the less-than sign not work as a replacement for cat in bash?

I heard about "useless use of cat" and found some suggestions, but the following outputs nothing in my bash shell. < filename Using cat works as expected though. cat filename I'm using Fedora ...
1
vote
3answers
314 views

the difference between '..' and “..” when I use ssh usr@ip 'pscp …'

My Server machine run Window,and it installed Cygwin. My Client machine run linux. In Clinent machine.I do this: [sikaiwei@login-1-2 v1.4]$ bash test.sh CHUN~19900405 ...
2
votes
1answer
414 views

what is wrong with this command? [closed]

I have this command in a shell script. I this command I am connecting to ftp server and reading a file path/download.txt to read further commands. sftp -v -oIdentityFile=/root/.ssh/filename ...