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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2
votes
1answer
60 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 ...
0
votes
3answers
62 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 ...
19
votes
2answers
825 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?
4
votes
1answer
118 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
130 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
50 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
votes
1answer
437 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
votes
2answers
154 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. ...
1
vote
3answers
62 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 ...
2
votes
2answers
61 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 > ...
5
votes
3answers
196 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 ...
1
vote
1answer
102 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 ...
2
votes
2answers
33 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 ...
8
votes
3answers
375 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? ...
5
votes
2answers
72 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 ...
2
votes
2answers
62 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', ...
0
votes
1answer
48 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
votes
2answers
31 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 ...
0
votes
1answer
18 views

paths for searching executables [duplicate]

My old xournal is 0.4.5, which is /usr/bin/xournal. I just installed a new version 0.4.8 by compiling from source to /usr/local/bin/xournal. When I call xournal directly from the terminal, it is the ...
3
votes
1answer
71 views

Is there a way to pass a variable from an awk statement to a bash function as an argument? [closed]

I am trying to look a for some specific values from (such as 1 or 4 and 2 or 3) a text file using an awk statement in a bash script. If this value is found in the file (within the awk statement), then ...
4
votes
3answers
260 views

awk with if statements

I am trying to print from a file using awk, but my output is empty. Here is my code so far accountNum=$1 while read -r LINE || [[ -n $LINE ]] ; do awk -F',' '{ if($1==accountNum) { print ...
14
votes
3answers
963 views

What does it mean to be “sh compatible”?

I've seen the phrase "sh compatible" used usually in reference to shells. I'm not sure if it also applies to the programs that might be run from within shells. What does it mean for a shell or other ...
10
votes
2answers
296 views

Strange difference between pwd and /bin/pwd

I added a symlink to the current directory with ln -s . aa. If I execute cd aa, and after that I executed pwd, the response is /home/sim/aa. But if I execute /bin/pwd it prints /home/sim (the current ...
3
votes
1answer
50 views

Grepping a variable

I've written a simple init script to start and stop a Python script as a service. I have to be explicit about the version of Python I'm running, because this is on a CentOS 5 box with Python 2.4 & ...
4
votes
3answers
160 views

Regex alternation/or operator (foo|bar) in GNU or BSD Sed

I cannot seem to make it work. GNU sed documentation says to escape the pipe, but that doesn't work, nor does using a straight pipe without the escape. Adding parens makes no difference. $ echo ...
2
votes
1answer
57 views

Renaming the files and move to other path

I need to rename the files given below and move to some other path 1234551abcde20140718023216001.txt.809047512.2014_07_07_13:47:44 000001abcde20140718023216001.txt.34568.001.2014_07_07_13:50:44 ...
4
votes
5answers
98 views

Add leading characters infront of string using printf or echo

How can I add leading characters to fill a string to a certain length? Assume I want to add zeroes infront of a string, if said string is shorter than 20 characters: printf '%020s\n' "$line" ...
0
votes
1answer
32 views

Must pass urls in quotes

I'm trying pass a URL to mpv for it to play it as a network stream. This can be done in bash with the following syntax: $ mpv http://myvideosite.com However, zsh wants to evaluate the URL as ...
1
vote
2answers
26 views

Shell is option given

I have a couple of arguments inside a list (array, e.g. $@) and I'd like to know if the option -v is in the list. In Python I would simply do: verbose = "-v" in sys.argv How do I achieve that in ...
2
votes
1answer
50 views

How can I get this script file's functions to load without having to source it every time? “command not found” (Bash/scripting basics)

How can I get this script file's functions to load without having to source it every time? I created a file foo with script functions I'd like to run. It's in /usr/bin, which is in the PATH. File ...
1
vote
1answer
54 views

Verify the length of a variable

I've to verify the length of variable read (my script limit to five the characters inserted), I think about something like this: #!/bin/bash read string check=${#string} echo $check if [ $check -ge 5 ...
2
votes
3answers
46 views

Looking for a way turn multiples commands with same parameter into a one liner

I sometimes end up doing things like: Example: from ~/blah $ mkdir ~/test-tmp $ cp * ~/test-tmp $ cd ~/test-tmp using the destination dir 3 times in a row. Isn't there a way to turn these into a ...
4
votes
1answer
52 views

What exactly is 'scrollback' and 'scrollback buffer'?

What are "scrollback" and "scrollback buffer" in programs like bash and screen, and how do they relate to the tty, the programs being run, and stdin/ stdout/ stderr? Here is the only definition of ...
6
votes
2answers
293 views

How to find out which program can open a given file?

Let's say I have a file thesis.pdf or picture.jpg Is there a command which returns a program to open this file with? I am aware of the command file, but it just returns the correct type of the file ...
1
vote
3answers
86 views

How do I Copy and Paste lines between a start and end keyword?

I have two text files, and I want to copy a bunch of lines from one to the other. File one has a list of packages, and I want to copy it to list two. This list of packages isn't at the start of file ...
4
votes
2answers
74 views

How to redirect stdout to a file and read from the same file simultaneously with another task?

I want to run a task (which takes quite a long time) remotely in Ubuntu Linux Bash via nohup and redirect stdout to a file, e.g.: nohup task > out.txt & From time to time I would like to ...
2
votes
1answer
53 views

Backslash with pipe in system command from awk

I want to invoke shell command from awk so I am using system() but when I am passing expression in I am getting error at backslash. Here is my expression echo "select * from abc limit 1;"| ...
0
votes
2answers
24 views

concatenate .out files

Can I combined multiple .out files with the cat command in bash or csh? Additionally I want only the header of first file to be concatenated and I was thinking of using the tail function for that. ...
2
votes
3answers
203 views

Shell script not executing

Not sure what is happening. Lets call script a.sh with the following /users/guru$ cat a.sh #! /usr/bin/ksh echo "Hello" date Execute with ksh. It gets done. /users/guru$ ksh a.sh Hello Tue Jul ...
0
votes
1answer
139 views

Bash script question - skip enter key press [duplicate]

Here is a portion of my script: read main_menu case "$main_menu" in "0" ) exit ;; "1" ) cp /etc/bamt/cgminer.conf.X11 /etc/bamt/cgminer.conf; sudo mine restart; ...
3
votes
2answers
110 views

Add arguments to bash -c

Let say that I want to run a command through bash like this: /bin/bash -c "ls -l" According to bash man page, I could also run it like this: # don't process arguments after this one ...
1
vote
1answer
37 views

Bundling of dependencies with shell scripts

Shell scripts often have to depend on tools that may not be installed on the users' computer. To circumvent this problem, many scripts have multiple fallbacks. IMO doing such things only leads to ...
4
votes
2answers
105 views

Get specific line from command output in awk

I have used pipeline to read specific record from impala shell.Here is what I got [cloudera@localhost ~]$ echo "select * from abc where key > 'a-26052014015400' limit 1;" | impala-shell Starting ...
15
votes
1answer
880 views

What does the @ (at) symbol before a filename mean in a curl command?

I am looking at an example of a curl command that uses the @ symbol before the filename to post data to the server. curl http://localhost/ --data-binary @file.txt What does this mean? Does it ...
4
votes
3answers
99 views

Write text messages between Unix and Windows

Is it possible to send text messages between two users of the same LAN, but the first running Windows with cmd and the second running Linux/Unix? I am not looking for an instant messaging service. I ...
4
votes
1answer
146 views

Keep getting the same result after “export PATH”

I am doing this: $ which cabal /usr/bin/cabal $ export PATH=$PATH:$HOME/.cabal/bin $ which cabal /usr/bin/cabal I expect to get /.cabal/bin/cabal for $ which cabal (this path exists) after this. ...
3
votes
2answers
86 views

Getting the current path in .desktop EXEC command

Im trying to make a .desktop file run a .sh which is stored in the same directory as the .desktop. The whole directory needs to be portable and moved from machine to machine. my run script is run.sh ...
2
votes
2answers
117 views

How to force watch to run under bash

The problem is that when watch is executed it runs sh and I get this error: sh: 1: func1: not found here is the code: #!/bin/bash func1(){ echo $1 } export -f func1 watch func1
3
votes
1answer
82 views

find files without extension

Let say I have: foo.txt bar baz.ooo If I use ls -1 !(*.*) then I'll get only bar on the output. Great, now I wish to have same results with find - some find -regex that will do the job. NOTE: ...
0
votes
0answers
28 views

How to return multiple select count in an array variable in shell

I have a 4 SQL count values which I want to return in an array record_count so that I can use that count values in some if statements later in the shell program. But I am not able to return the values ...