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, …).

learn more… | top users | synonyms (1)

36
votes
4answers
4k views

How to use `which` on an aliased command?

Like most users, I have a bunch of aliases set up to give a default set of flags for frequently used programs. For instance, alias vim='vim -X' alias grep='grep -E' alias ls='ls -G' The problem is ...
17
votes
7answers
2k views

how to glob every hidden file except current and parent directory

I want to glob every hidden file and directory, but not the current (.) and parent directory (..). I am using bash. Observe current behaviour: $ ls -a . .. ...a ...aa ..a ..aa .a .aa .aaa ...
1
vote
1answer
85 views

Canot remove symlinks: after reboot, symlinks re-appear

Using ssh from BusyBox, I cannot remove symlinks: after rebooting the device, symlinks re-appear. ls -la shows that symlinks have been removed, but after rebooting device they re-appear again. Those ...
1
vote
1answer
27 views

Can you further integrate and present sequential moreutils vipe command output in vim using successive splits etc?

I have used the moreutils suite a few times and I find it makes you think further about base utilities and is insightful(and fun). For instance, vipe allows running an editor - like vim - in the ...
1
vote
3answers
78 views

How to get a response from any URL?

I have been asked to write a shell script To check if a URL is UP/Working or not for my Project. I tried to find some hints over the internet, but whatever I got is about checking whether the URL ...
1
vote
3answers
63 views

Why is ls command slow to interrupt on NFS directory with lots of files?

I noticed in directories with lots of files on NFS if I do ls * then hit Ctrl-C it can take a while ( say 20 seconds ) before ls comes back. Why? Can ls command be fixed to be more responsive?
0
votes
2answers
47 views

Getting expr: syntax error on index [duplicate]

Using this OF=$(ps fax | grep 'php-fpm: master process' | awk '{print $1}') IDX=`expr index $OF ' '` I get an error. The results of the $OF variable are: 27797 27495 What is the error here? I ...
3
votes
5answers
239 views

How to use a shell variable inside sed's s command? [duplicate]

we know that we can get the value of a variable using $ sign: x=3 echo $x 3 Is there other ways that we can use to get the value without using $ sign. I'm asking this because $ sign is a special ...
3
votes
1answer
39 views

Fine-tune LS_COLORS for directory suffixes?

I’m fine customizing most settings in LS_COLORS. I don’t need help customizing the colors for different file suffixes. What I would like to do is configure special colors for certain directories, ...
3
votes
1answer
40 views

Escape closing parentheses from URL with firefox -remote

I have this command (for detailed info see Shortcut to google selected text): sh -c 'firefox -remote "openURL(http://www.google.com/search?q=$(xsel),new-tab)"' But when I select a text which ends ...
3
votes
1answer
29 views

Can I make “less” execute arbitrary commands with a single key sequence?

The crux of my question is stated in the title. Reading the less and lesskeys manpages, I have created a file containing: ^B shell touch ~/testfile and run it through lesskey to generate ...
8
votes
2answers
2k views

“trap … INT TERM EXIT” really necessary?

Many examples for trap use trap ... INT TERM EXIT for cleanup tasks. But is it really necessary to list all the three sigspecs? The manual says: If a SIGNAL_SPEC is EXIT (0) ARG is executed on ...
19
votes
12answers
3k views

Remove duplicate $PATH entries with awk command

I am trying to write a bash shell function that will allow me to remove duplicate copies of directories from my path environment. I was told that it is possible to achieve this with a one line ...
5
votes
2answers
2k 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) ...
0
votes
2answers
25 views

moving a process to fg and bg [duplicate]

Suppose I run a process in the background likw ./script &, I can bring it to foreground by running fg. However, is there a way to move it back to background without stopping it (as in ctrl+z) or ...
2
votes
1answer
587 views

Gnome + Linux: GUI apps don't inherit PATH from parent console apps

In Gnome, don't GUI applications inherit the PATH of the shell process that launches them? Apparently, GUI applications see only the PATH specified in ~/.profile. No issues with console applications, ...
0
votes
2answers
40 views

Determining the exit status of the “return” built-in

I was reading about traps, but only return works for me in my shell script, so was wondering what status or code it returns, so what I tried is, #!/bin/bash seeOutput=`return` echo $seeOutput It's ...
-3
votes
1answer
40 views

to run script over several folders? [duplicate]

Currently I have a script that can run only in a single folder. #!/bin/bash for file in ls -1 *.jpg|sort -t . -n -k 3 do echo "compute ./scripName $file" ./scriptName $file done Question: I ...
0
votes
0answers
76 views

Cant ssh, connection terminates immediately with exit status 254

The most recent thing I remember is changing the soft and hard memlock ulimit to unlimited. Now I cant ssh into the machine. This is the ssh log. Authenticated to IP ([IP]:22). debug1: channel 0: ...
128
votes
2answers
23k views

Difference between nohup, disown and &

What is the difference between $ nohup foo and $ foo & and $ foo & $ disown
6
votes
2answers
178 views

How many commands can be queued up with control operators?

I have been reading up on control operators, and I was wondering if there was a limit to how many commands you could line up with control operators, such as ||, && and ;. In addition, is ...
7
votes
0answers
74 views

regarding portable sed -e… d b or ! b?

In this edit Stéphane Chazelas POSIXifies (again) my sed formatting by inserting an -expression break and another -expression statement. Now, I might just ask him why in the comments, I suppose, but ...
1
vote
2answers
58 views

Why does sudo ignore aliases?

I am running Ubuntu 10.04 and I use upstart for daemon management. My enterprise application is run as a daemon and must be run as root because of various privileges. E.g.: sudo start ...
5
votes
3answers
190 views

sed ranges aren't always able to match only one line

Consider the following range: 1,/pattern/. If pattern matches on the first line, the range matches for the whole file: $ cat 1.sh #!/usr/bin/env bash set -eu seq 1 4 | sed -rn '1,/'"$1"'/p' $ ./1.sh ...
5
votes
4answers
104 views

Is it shell portable to run a command on the same line after variable assignment?

Is there any standard that covers the portability of running a command after variable assignment on the same line? APPLE="cider" echo hi How portable is something like that? Where will it work and ...
1
vote
1answer
39 views

Compare file size of multiple files in an array [closed]

Scenario: Ftp site has 100s of files. Once a day, all the .gz files are copied to an AWS site then renamed. Only the date is kept in the file name. Some of the files corrupted during copy. A txt ...
1
vote
1answer
17 views

What standard shell command can evaluate escaped Unicode in a stream?

I'm looking for a pipeable command that will convert substrings in the form of ‘\unnnn’ to the actual characters. For example: $ echo 'co\u00ebfficient' | what_command coëfficient
16
votes
8answers
2k 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 ...
4
votes
2answers
79 views

Write variable containing large text with \n to a file with common shell interpreters. How do you do it?

Environment: linux shell or better, ash shell in busybox (example system: Openwrt). Given a string variable with large text "${a}" constructed in this way: for index in $(seq 1 40000); do #it is ...
6
votes
8answers
7k views

Using sed to convert newlines into spaces

Say I have a shell variable $string that holds some text with several newlines, e.g.: string="this is a test" I would like to convert this string into a new string new_string where all line breaks ...
1
vote
2answers
94 views

Pass a command to ROOT from a shell script and having it stay open

I am writing a bash script to perform some analysis using the program ROOT. I want to run some initial command to load the result of the analysis, then continue using ROOT interactively. The analysis ...
1
vote
1answer
26 views

Save views in multiple screen terminals

As I do in default single view screen terminal of ubuntu; gnome-terminal \ --tab-with-profile=Default --working-directory="some dir" --title="some title" \ --tab-with-profile=Default ...
4
votes
0answers
36 views

Show error messages and information that a program was killed on another terminal [duplicate]

If I open a program, say evince, from the GNOME GUI, it is not attached to a terminal. If I send it a signal, it acts accordingly but nothing shows up in my terminal. If I were to open it in a ...
0
votes
1answer
485 views

Proper escaping of double quotations for curl post data?

I'm trying to test out a server, by sending it JSON data and reading the response. I need to POST data like {"item":"value with spaces"} but when I use curl I find that it sends the backslashes as ...
3
votes
6answers
1k views

How to use the sed command to only show the first column and last column in a text file

I need some help to figure out how to use the sed command to only show the first column and last column in a text file. Here is what I have so far for column 1: cat logfile | sed 's/\|/ /'|awk ...
-4
votes
1answer
39 views

What is the significance of the the leading “4” before the listing of modified files?

After running the following command: find /Users/UserName/Documents -type f -mtime -1 -print0 | xargs -0 du -sk | sort -nr I receive the following output: 4 ...
106
votes
15answers
42k views

How to do integer & float calculations, in bash or other languages/frameworks?

Using echo "20+5" literally produces the text "20+5" What command can I use to get the numeric sum, e.g. 25 in this case. Also, what's the easiest way to do it just using bash for floating point, ...
-1
votes
0answers
24 views

Shell parameter substiution [duplicate]

I am very confused between $n,$* and $@. All of them seem to do the same thing. I find $* and $@ almost similar for some reason.Can anyone help me bifurcate how the arguments are read and processed ...
9
votes
6answers
1k views

How do you remember command options? [closed]

I am curious to know what trick you use to remember options for various commands? Looking up man pages all the time is time consuming and not so cool!
1
vote
2answers
76 views

Shell syntax question with difficult parameter expansion

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 ...
0
votes
1answer
523 views

How to execute Netscaler commands through a remote machine via SSH connection

I have been trying to execute some NetScaler commands like "bind" & "unbind" through a Linux Box via an SSH Connection. Now the Problem is, Manually we are able to enter & execute commands on ...
1
vote
2answers
36 views

awk - read program AND input from the standard input?

Is it possible for awk to read the program and the input from the standard input? I would like to be able to pipe a file to the following function. process_data () { awk -f - <<EOF {print} ...
5
votes
6answers
429 views

How can I reverse the first part of a sentence?

I know that I can reverse any sentence: echo "a,b,c,d" | rev but what if I want to reverse only the first part of a sentence, I have tried this: echo "a,b,c,d Access" | rev and I get this: sseccA ...
15
votes
6answers
13k views

How to match case insensitive patterns with ls?

I would like to list all files matching a certain pattern while ignoring the case. For example, I run the following commands: ls *abc* I need to see all the file that have "abc" as a part of the ...
2
votes
1answer
424 views

Xubuntu 12.04: slow login

I'm running Xubuntu 12.04, and after I ran the update, my login started slowing down big time. I've dabbled a little bit with the programs in Settings -> Settings Manager -> Session and Startup, and ...
-1
votes
1answer
27 views

bash: adduser: command not found on centOS

I installed centos 5.5 on my vmware 8 recently and i am trying to add a new user on the system. I am unable to add the user unless i use su - option. I believe it has to do something with path not set ...
7
votes
1answer
1k views

Can't indent heredoc to match nesting's indent

If there's a "First World Problems" for scripting, this would be it. Mainly asking because I feel like I should know how to get around it if I need to. I have the following code in a script I'm ...
5
votes
1answer
44 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. ...
4
votes
4answers
241 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 = ...
4
votes
4answers
63 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 ...