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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2answers
74 views

Listing folder contents during cd command

I might be mistaken here, but I was watching someone navigate using the cd command, and without actually executing it, they were able to show the folder contents of the current folder. So if I type ...
2
votes
3answers
3k views

Call sed to replace a string stored in a bash variable

I want to expand a variable in bash with sed or awk. This variable is an array. For example, the script must delete strings contained in array. I tried ARRAY1=( string1 string2 string3 ) sed -i ...
0
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2answers
62 views

copy and rename script

Directory A: 1111111_1.pdf 2222222_1.pdf 1234567_1.pdf Directory B: abcdefg.pdf zzzzzzz.pdf 1234567.pdf 1111111.pdf 2222222.pdf ...
8
votes
4answers
4k views

exit shell script from a subshell

Consider this snippet: stop () { echo "${1}" 1>&2 exit 1 } func () { if false; then echo "foo" else stop "something went wrong" fi } Normally when func ...
26
votes
8answers
46k views

How can I run a cron command with existing environmental variables?

How can I run a cron command with existing environmental variables? If I am at a shell prompt I can type echo $ORACLE_HOME and get a path. This is one of my environmental variables that gets set in ...
9
votes
4answers
332 views

Unexpected EOF and syntax error

I am currently writing my third ever shell script and I have run into a problem. This is my script so far: #!/bin/bash echo "choose one of the following options : \ 1) display all current users \ ...
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5answers
1k views

bash event not found trying to match and exclude parenthesis in grep

In a very long line I'll summarize with: (foo),(bar,baz(word,right),(end) I want to print only: (bar,baz(word,right To match the second parenthesis, I exclude the word that follows the ...
4
votes
3answers
226 views

Script to compare 2 input paramters and show shared letter(s)

I am writing a script that I want a user to enter two separate words, and the result to show which letter the two words share. For instance ./share Cat Rat - would return shared letters: "a" and "t". ...
8
votes
3answers
8k views

How to select specific processes with 'top'?

In case of one program having multiple instances, running pidof program gives: `1 2 3` top -p accepts comma-delimited arguments: 1, 2, 3. This means that top -p `pidof program` won't work: ...
28
votes
4answers
2k views

What are the responsibilities of each Pseudo-Terminal (PTY) component (software, master side, slave side)?

I am trying to figure out how a tty works1 (the work-flow and responsibilities of each elements). I have read several interesting articles about it, but there are still some blurry areas. This is ...
4
votes
1answer
121 views

Length of argument inside a function of an sh script

I have a FreeBSD 9.3 RELEASE server and I am trying to write a shell script using sh. I am trying to get the length of a variable that is passed to a function in a shell script, like so: #!/bin/sh ...
2
votes
1answer
152 views

auto complete in shell script

My folders are named by date: 20140930DoingShellStuff 20140931HopefullyShellIsDone ... What I want to do is write a shell script to auto cd into the folder which corresponds to the current date. I ...
0
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1answer
78 views

Unix: What happens if I enter ls -d [2-q]*

Would it just ignore the bit after the -d option since you cant arrange characters lexically between 2 and q?
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votes
1answer
474 views

Delete all mails from inbox using linux command prompt

How can I delete emails from an individual email account? e.g. how can I empty userxyz@mydomain.com? I know the following: /var/spool/mail/mydomain /var/mail/mydomain I have many inboxes some of ...
22
votes
2answers
7k views

Quoting within $(command substitution) in Bash

In my Bash environment I use variables containing spaces, and I use these variables within command substitution. Unfortunately I cannot find the answer on SE. What is the correct way to quote my ...
0
votes
1answer
36 views

Replace copyrights recursively [duplicate]

I have many files under the current directory. Each file contains copyrights headers like, # # Copyright 2013 Company, Inc. All rights reserved. This software # is property of Company, ...
3
votes
4answers
650 views

How to return a background task to be in the foreground?

Well, the title does not say much, but I would like to know how to stop a running process after appending it with &. For example, I would like to install software foo. Now, assume, foo has many ...
6
votes
1answer
168 views

cd and ls behave differently when inside a softlink to a dir

When we cd into a dir via its softlink, i observe: ls .. will show the content of the parent dir of the linked dir, while cd .. will go under the parent dir of the softlink. Why are they different? ...
10
votes
1answer
302 views

Why does `postgres` require a shell?

In my Debian Wheezy systems, I noticed that the postgres user 'postgres', the "PostgreSQL administrator", uses /bin/bash as shell. However, I cannot figure out why this is needed. Changing this to ...
3
votes
1answer
50 views

Read target of symlink and increment target by one

I have a folder structure that looks like this /some/folder/1 /some/folder/2 ... and a symlink current that links to one of the folders. Is it possible and when how to read the target of the link, ...
-1
votes
1answer
128 views

Redirect a directory as input to a script and output to a file

I want to use a directory name as a parameter for a pre-made script. Then the output goes into a newly made file in the home directory. It involves pipe/redirection. How do I do that? read dir $dir ...
1
vote
1answer
86 views

Run Comand on all files (folders ad subfolders) [duplicate]

All, I have a lot of PDF files. Does there exist a way to apply to all PDFs in folder and sub-folders at one time? Example, I have: /pdf/test/pdfa.pdf /pdf/example/aa/test.pdf I'd like to apply ...
1
vote
1answer
350 views

How does Git change the shell prompt in Aptana Studio's Cygwin Terminal?

I'm running Aptana studio 3.3.2. The command echo $SHELL outputs /bin/sh. However there is no value for the PS1 environment variable which I would like to inspect. I cannot there is no .bash_profile ...
0
votes
1answer
64 views

I ran `zsh -v` and now I have no shell history [closed]

I just installed zsh today to try it out. I was trying to check my zsh version and I accidentally entered zsh -v which is the verbose option. Now I can't seem to use reverse search on history. How ...
4
votes
1answer
126 views

Problem combining -or and -exec with find command

I'm finding that when I use find's -or operator in combination with -exec, I don't get the result I expect. When searching for .cpp and .h files, the command works as expected if I don't use -exec: ...
3
votes
2answers
239 views

leaking memory with shell script and tty [closed]

I'm running a shell script on a raspberry pi to communicate with a arduino. Every hour my ram gets used up by about 50 megabytes more. The script itself just connects to ttyACM0 (the arduino's usb ...
8
votes
2answers
361 views

Why is a variable visible in a subshell?

The Learning Bash Book mentions that a subshell will inherit only environment variables and file descriptors, etc., and that it will not inherit variables that are not exported: $ var=15 $ (echo ...
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votes
6answers
2k views

How to change to normal user in the command line when logged in as the root user?

I log into an system through root via ssh. How do I become the normal user or another user on the system?
5
votes
4answers
573 views

Is there a difference between read, head -1, and sed 1q?

The following commands seem to be roughly equivalent: read varname varname=$(head -1) varname=$(sed 1q) One difference is that read is a shell builtin while head and sed aren't. Besides that, is ...
3
votes
3answers
252 views

Method for storing/remembering one liner commands

Often when configuring and adjusting unix-based systems I use a lot of one-line commands that are difficult to remember. For example, to determine what version of ntp (the time server) is running, you ...
5
votes
2answers
825 views

How to capture ordered STDOUT/STDERR and add timestamp/prefixes?

I have explored almost all available similar questions, to no avail. Let me describe the problem in detail: I run some unattended scripts and these can produce standard output and standard error ...
5
votes
3answers
1k views

Is there any CLI/terminal slideshow app?

I'm asking myself: is there, on linux, any software that can build and show simple slides on terminal, like the slides you make on Libreoffice Impress (but way more simple)? This would be a great ...
3
votes
2answers
582 views

Interacting with a running interactive console program from a different process

I have a console program with an interactive shell, similar to say, the Python interactive shell. Is there an easy way to start this interactive program A and then use another program B to run A? I ...
26
votes
4answers
3k views

difference between “function foo() {}” and “foo() {}”

I can define bash functions using or omitting the function keyword. Is there any difference? #!/bin/bash function foo() { echo "foo" } bar() { echo "bar" } foo bar Both calls to functions ...
1
vote
1answer
818 views

/bin/sh: error importing function definition for `some-function'

I encountered this error when updating bash for the CVE-2014-6271 security issue: # yum update bash Running transaction (shutdown inhibited) Updating : bash-4.2.47-4.fc20.x86_64 /bin/sh: error ...
0
votes
1answer
1k views

Copying files with multiple extensions

I would like to copy files with multiple extensions to a single destination directory. For example, I can use the following command to copy all .txt files in the working directory to a directory ...
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votes
2answers
6k views

How to delete a file in Arch console?

pacman stopped working and asked me to delete a file if "another package manager isn't working". What is the file for deleting files?
2
votes
4answers
205 views

Bash - How do I loop through subdirectories and extract the files

I have a directory called 10K_TIF (main directory). Within this main directory are multiple sub-directories each containing tif images. I want to read each TIF image and extract its path using a bash ...
1
vote
1answer
404 views

Interactive Shell Session from Java

I want to run a series of commands from Java. I came across few forums that explain how to execute multiple commands using getRuntime().exec(command) and defining command as String[]. But I want to ...
0
votes
4answers
1k views

How to get process id of a command

We are running some command in batch mode. We need to do some more tasks once the existing command is done, so we need to wait until this command is done. For example: bsub -q gui -I calibre -drc ...
0
votes
2answers
49 views

Rsync'ing system, exclude doesn't seem to work

I'm trying to make a full filesystem backup of a server through rsync, following this guide. I'm using the following command: rsync -aAXH --progress --delete --stats --exclude={\ "/dev/*",\ ...
0
votes
1answer
94 views

How to move cron commands into a script?

Can someone give me an example that shows how to put Cron commands into a script? Using these commands as an example: find /home/network/public_1 -type f -ctime -1 -exec ls -ls {} \; find ...
1
vote
1answer
65 views

Is it possible to create a Linux environment without a traditional command shell?

i.e. Using something like IPython, re.pl, or somesuch as a login shell, instead of bash/ksh/etc. Using initscripts, etc. written in Python or some other scripting language, and making no use of ...
5
votes
1answer
94 views

Make program in a pipe to think it has tty

Test environment: $ mkdir testdir $ cd testdir $ echo | tee "file name" Now, ls will print file?name (under Ubuntu GNU bash, at least), while ls | cat will print file and name in separate lines. ...
3
votes
2answers
854 views

Assign Subshell background process pid to variable

I am currently starting a background process within a subshell and was wondering how can I assign its pid number to a variable outside the subshell scope? I have tried many different ways but MYPID ...
6
votes
2answers
2k views

How to trigger error using Trap command

I am using Ubuntu 12.04.2. I am trying to use "trap" command to capture abnormal or error in my shell script but I am also trying to manually trigger "Error" exit. I have tried exit 1, but it won't ...
1
vote
1answer
29 views

Icon stops loading after the application restarts

I have a application which uses "self-restart" mechanism. It kills itself and runs again. When I run it first time (with .desktop file) it loads its icon correctly. The problem is that when it ...
2
votes
3answers
728 views

How to find md5sum of files on remote machines by doing ssh?

I am running my below shell script on machineC which gets the md5sum of my files in my PRIMARY directory in machineC itself. #!/bin/bash export PRIMARY=/data01/primary for entry in "$PRIMARY"/* do ...
1
vote
1answer
292 views

du skip symbolic links

I cannot find an example of what I want to do and, from what I'm reading, the default behavior of du on my system is not the proper default behavior. If I ls my /data folder, I see (removing the ...
2
votes
2answers
117 views

List of subdirectories that contains a particular file name

I am wondering if i can do this in a single shell command. I am in home directory and want to find a list of subdirectories that contains a particular file. The file name and the depth is always ...