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Questions tagged [shell]

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, …). For shell scripts with errors, please check them in http://shellcheck.net before posting here.

4
votes
1answer
9k views

Remove files, which provided by pipe

I have this command chain: find . -print | grep php | xargs grep 'eval' -sl | xargs wc -l | grep ' [1-2][0-9] ' This provide me this output: 14 ./includes/js/calendar/lang/vgju.php 18 ./includes/...
25
votes
6answers
14k views

How do I recursively check permissions in reverse?

There's a command, I think it comes with apache, or is somehow related to it, that checks permissions, all the way down. So if I have /home/foo/bar/baz it will tell me what the permissions are for baz,...
15
votes
6answers
13k views

Can I make `cut` change a file in place?

The man page doesn't give me much hope, but I'm hoping it's an undocumented (and/or GNU-specific) feature.
262
votes
6answers
25k views

What's the difference between $(stuff) and `stuff`?

There are two syntaxes for command substitution: with dollar-parentheses and with backticks. Running top -p $(pidof init) and top -p `pidof init` gives the same output. Are these two ways of doing the ...
17
votes
3answers
33k 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: top:...
4
votes
4answers
8k views

How do I check if a file already has line with “contents” in it?

I need to know if a file aready has line with contents X in it, if not append line. here's the code I've tried. if ! $(grep 'eval $(perl -I$HOME/foo/lib/perl5 -Mlocal::lib=$HOME/foo)' ~/.bashrc) then ...
9
votes
3answers
590 views

Doing two things with output from a command

I have a program texcount that outputs the number of words in my LaTeX document. I can also pipe the output of this to sed to make the newlines TeX linebreaks and write this to a file which I can then ...
3
votes
4answers
5k views

Shell script error message

I am trying to learn shell scripting by reading linuxcommand.org. For some reason I keep getting the error "Not Found", even though it runs all the commands. The error codes I get are: ...
4
votes
1answer
1k views

scp, globbing, and different shells

The other day at work I tried doing scp remotehost:~/*.txt . and I received an error about the *, *.txt file not found sorry, not at work and I forget the exact error on my workstation I run zsh 4....
5
votes
4answers
7k views

How can I search for a file with fixed name length using ls?

In a directory, I have files like lazer_100506 lazer_100707 lazer_091211 lazer_110103 lazer_100406_temp lazer_100622#delete etc How can I get a listing of only the first four files? $ ls lazer_.......
32
votes
3answers
4k views

Can a bash script be hooked to a file?

I want a script to sleep unless a certain file is modifed/deleted (or a file created in a certain directory, or ...). Can this be achieved in some elegant way? The simplest thing that comes to my mind ...
3
votes
1answer
9k views

cURL access HTTPS website

I trying to access the following site with cURL. (https://www.fleetagent.be) I have cURL configured with the following switches -L -k --proxy [username:password] I get the following error. What ...
16
votes
3answers
80k views

How can I concatenate a shell variable to other other parameters in my command lines ?

How can I concatenate a shell variable to other other parameters in my command lines? For example, #!/bin/sh WEBSITE="danydiop" /usr/bin/mysqldump --opt -u root --ppassword $WEBSITE > $WEBSITE....
5
votes
1answer
1k views

Intercept “command not found” error in zsh

Is there a way to intercept the "command not found" error in ZSH? I've seen this is possible in bash apparently, but I couldn't find anything about doing it in zsh.
5
votes
2answers
7k views

Count the number of words of particular length from a file

I've used the below command to count the number of words in a file: tr ' ' '\n' < Filename | grep -c "WORD" This returns the word list with counter. Now I want to count the number of words of a ...
31
votes
3answers
32k views

How do I tell a script to wait for a process to start accepting requests on a port?

I need a command that will wait for a process to start accepting requests on a specific port. Is there something in linux that does that? while (checkAlive -host localhost -port 13000 == false) ...
4
votes
4answers
4k views

Xargs and rm with a *

I am trying to execute the following command ls -d a* | xargs -i sudo rm -rf {}/* The problem is that when I add the /* part the command does not work. I want to remove the directory contents (not ...
2
votes
1answer
370 views

kdialog --getsavefilename target/directory?

When I use kdialog --getsavefilename /path/to/specific/folder/, it opens folder/'s parent directory, not folder/ itself. How do I get it to start where I want it to?
6
votes
3answers
7k views

Invoking pushd in a shell script

I have a simple script that I want to invoke 'pushed' followed by another command. But the 'pushd' command inside the script doesn't seem to stick past the script. What's a way to make this execute ...
19
votes
2answers
9k views

How do I test to see if an application exists in $PATH?

I'm trying to write all of my sh startup/env scripts to work with as much DRY and as much: "works on every *nix I clone it to", as possible. This means making sure that if I try to run code that's not ...
2
votes
1answer
265 views

Why does the local::lib shell code use eval and $()

using local::lib requires you to add a line to your ~/.shellrc eval $(perl -I$HOME/perl5/lib/perl5 -Mlocal::lib) I don't understand what the point of using eval, and encasing the statement in $() is....
4
votes
1answer
154 views

How can I run keychain in a way that only has the first shell prompt for keys on startup?

I open multiple shell tabs when I start KDE, and I've just added keychain to my ~/.shellrc the problem is that all the tabs prompt for key passwords when I login. This is quite annoying to do this. Is ...
21
votes
4answers
3k views

keep duplicates out of $PATH on source [duplicate]

I have the following code that's source-d by my .shellrc PATH="${PATH}:${HOME}/perl5/bin" PATH="${PATH}:${HOME}/.bin" export PATH but if I make changes to other code and then source this file, my ...
12
votes
1answer
11k views

Leaking file descriptors

What does it mean if file descriptor leaking File descriptor 6 (socket:[901758]) leaked on lvextend invocation. Parent PID 10035: /bin/zsh File descriptor 9 (/dev/pts/1) leaked on lvextend ...
10
votes
5answers
12k views

sh startup files over ssh

I have some important commands I need to execute before any sh shell starts. This is required for passing SSH commands in the SSH command (ssh host somecommand) and other programs that run commands. ...
133
votes
4answers
44k views

$VAR vs ${VAR} and to quote or not to quote

I can write VAR=$VAR1 VAR=${VAR1} VAR="$VAR1" VAR="${VAR1}" the end result to me all seems about the same. Why should I write one or the other? are any of these not portable/POSIX?
7
votes
2answers
3k views

TAB autocomplete in Bourne Shell

I don't know how to get the TAB key to autocomplete filenames, commands, or anything at all. I'm on a Unix-like system (OS/390) and depend on several scripts that work in sh (Bourne shell, not BASH),...
40
votes
1answer
14k views

Is it possible to have vim key bindings in terminal?

I'm getting used to vim bindings (like pressing w to go to word, dw to delete a word, and such) and it's modes (insert, normal, visual), and, out of curiosity would like to know: is there some kind of ...
16
votes
4answers
27k views

find-command for certain subdirectories

Let's say I have a directory dir with three subdirectories dir1 .. dir3. And inside I have many files and other subdirectories. I'd like to search for a file inside, say with a *.c ending, but I'd ...
22
votes
5answers
57k views

Adding numbers from the result of a grep

I run the following command: grep -o "[0-9] errors" verification_report_3.txt | awk '{print $1}' and I get the following result: 1 4 0 8 I'd like to add each of the numbers up to a running count ...
9
votes
3answers
7k views

How do I use redirection with sudo [duplicate]

Possible Duplicate: Redirecting stdout to a file you don't have write permission on Yeah I could (and probably will) just escalate to root, but I'd like to know why this doesn't work? sudo ...
40
votes
5answers
132k views

How to pass the output of one command as the command-line argument to another?

So I have a script that, when I give it two addresses, will search two HTML links: echo "http://maps.google.be/maps?saddr\=$1\&daddr\=$2" | sed 's/ /%/g' I want to send this to wget and then ...
30
votes
4answers
12k views

Quoting in ssh $host $FOO and ssh $host “sudo su user -c $FOO” type constructs

I often end up issuing complex commands over ssh; these commands involve piping to awk or perl one-lines, and as a result contain single quotes and $'s. I have neither been able to figure out a hard ...
13
votes
2answers
15k views

Rsync two file types in one command?

How to write those into one line, also without repeat the same path? rsync -a root@somewhere:/folder/remote/*.txt . rsync -a root@somewhere:/folder/remote/*.jpg .
17
votes
4answers
19k views

Creating a user who cannot get an interactive shell

What are interactive and non-interactive shell? Questions: Create a user john who should not get an interactive shell. How can we do this?
74
votes
12answers
52k views

determining path to sourced shell script

Is there a way for a sourced shell script to find out the path to itself? I'm mainly concerned with bash, though I have some coworkers who use tcsh. I'm guessing I may not have a ton of luck here, ...
4
votes
1answer
495 views

Set ls color listings based on regex instead of globbing

Is it possible to set regex patterns for color matching in the LS_COLORS variable? So instead of just *.jpg=38;5;220 Can I do \.(jpg|gif)=38;5;220 That's just an example, I'd like to get more ...
38
votes
15answers
21k views

Object-oriented shell for *nix

Preface: I love bash and have no intention of starting any sort of argument or holy-war, and hopefully this is not an extremely naive question. This question is somewhat related to this post on ...
35
votes
4answers
8k views

aliasing cd to pushd - is it a good idea?

Is it a good idea to use the following alias: cd() { pushd $1; } in bash? I think this would be very useful, since I can then use a series of popds instead of just a cd - once. Is there any ...
23
votes
1answer
3k views

Is there a way to redirect a program's output and still have it go to stdout?

Okay. If I wanted to redirect the output of a program to a file, I'd do something like this prog > file If I wanted to redirect both stdout and stderr to that file, then I'd do prog > file 2&...
3
votes
5answers
4k views

Does $SHELL store the path to the default shell in Linux?

My administrator says that my default shell is set to bash, but $ echo $SHELL /bin/csh $ Is the default shell related to the SHELL variable at all? Is not, what is the variable used for?
1188
votes
9answers
312k views

What is the exact difference between a 'terminal', a 'shell', a 'tty' and a 'console'?

I think these terms almost refer to the same thing, when used loosely: terminal shell tty console What exactly does each of these terms refer to?
29
votes
3answers
11k views

ls command: what does the first line mean?

When I do ls -l I get this: calico@A000505:~/Documentos$ ls -l total 2020 -rwxr-xr-x 1 calico calico 8559 2010-11-16 11:12 a.out -rwxrw-rw- 1 smt smt 2050138 2010-10-14 10:40 Java2.pdf -...
9
votes
1answer
1k views

What steps does the system go through when handling an SSH connection?

What steps does the system go through when handling an SSH connection? We try to log in via ssh sshd starts pam and pam module to authenticate us Depending on pam configuration, we need to provide ...
11
votes
1answer
3k views

How do I redirect output to cd?

Is it possible to redirect a command's output to cd? For example, I searched for a directory using locate and got the path to it. Now, instead of writing a cd path, can I redirect the locate output to ...
35
votes
1answer
8k views

Aliases vs functions vs scripts

This site says, "Shell functions are faster [than aliases]. Aliases are looked up after functions and thus resolving is slower. While aliases are easier to understand, shell functions are preferred ...
7
votes
2answers
364 views

How is a graphical application started from a bash session connected to that bash session?

When I start a graphical application from a terminal running bash, that application is somehow connected to that bash session. For example, when the applications dumps some text it will appear in the ...
550
votes
3answers
223k views

Difference between nohup, disown and &

What are the differences between $ nohup foo and $ foo & and $ foo & $ disown
1
vote
1answer
578 views

CH3MNAS Fun Plug and NZBget. Cannot launch NzbGet 0.7, word unexpected

I have un-tarred the nzbget0.70 debug version and have put it in the /ffp/bin dir. and I have a config file in the /ffp/etc/ dir but when I try to run it, I get the following: root@NAS:/mnt/HD_a2/...
60
votes
5answers
40k views

How to pass parameters to an alias?

For bash script, I can use "$@" to access arguments. What's the equivalent when I use an alias?