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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4
votes
2answers
127 views

What is the syntax for passing the output of a command to xargs?

As an example I am using xdotool to obtain the list of windows on my desktop, which outputs a list of numbers, one on each line. An example command for that is: xdotool search --name "a_program", ...
2
votes
1answer
132 views

What is the difference between filename=${1:-/etc/hosts} and filename=/etc/hosts? [duplicate]

What is the difference between filename=${1:-/etc/hosts} and filename=/etc/hosts? For example: filename=/etc/hosts if [ -r "$filename" ] && [ -s "$filename" ]; then md5sum $filename ...
1
vote
3answers
39 views

How do I set a file's mtime in epoch format?

I know how to get a file's mtime in epoch format: stat --format=%Y <file> But I have not been able to figure out how to set a file's mtime in epoch format. The touch(1) man page appears to ...
2
votes
3answers
45 views

Get the last minute dated lines from list

If I have an input file with a list of users and their dates they were last signed in, how can I select with a sort | awk function the last minute lines? The dates are written in a +%H:%M:%S format. ...
1
vote
3answers
169 views

How to read the file line by line and to print the previous line where the file contains a single token

For example my file is like: 59 6 18 2014 169 7 14 2 7671912 7849744 201 4 60 6 19 2014 170 5 49 2 7671912 7849744 201 5 61 6 20 2014 171 6 8 2 7671912 7849744 201 6 62 6 23 2014 174 5 3 2 7671912 ...
0
votes
4answers
124 views

Bash if conditions of variables within intervals

I have some data spread over time intervals, and I want to take some of those data within the time intervals. For example, I have data at times within 1..9, 11..19, etc., and I want to take data ...
1
vote
5answers
88 views

How to copy a file from a remote network to the local desktop

So I used SSH to remotely login to another computer on a network. I have many files that I would like to copy over to my local desktop. I am trying to follow this How-to : However, I think one ...
0
votes
2answers
30 views

Simple server that triggers script and responds

I need to have a very simple server running that can: Take rest call. It triggers a script when a call is made The script checks if database is running or not. If running then reply back to client ...
3
votes
1answer
42 views

Is there a single '03 registered UNIX which can't do rm — -foo at this point?

I'm trying to dispel this uncertainty I have about the use of the double-dash (two hyphens, --) as an end of options delimiter(as opposed to a long option prefix). It's possible some confusion arose ...
8
votes
2answers
103 views

Weird SSH issue, ssh works with -t but freezes without it

When I ssh into one of my servers, it seems to log in, but then hangs before giving me the prompt (message debug2: shell request accepted on channel 0 is the last log entry). Though the odd thing is ...
19
votes
2answers
763 views

Tilde (~) inside working unix directory

So, Im working in a UNIX environment and I noticed that inside my working directory, which is miles miles away from my UNIX home, there is a ~. Now, once in the past, I did rm -rf ~ from my working ...
1
vote
3answers
41 views

List files in a directory with a certain extension

I created a file called ~/usrlibs.txt, which contains the number of files that begin with lib and end .a found in the /usr/lib directory. I tried: ls -l /usr/lib/lib .a | wc -w > ~/usrlibs.txt ...
2
votes
3answers
38 views

Reuse similar flags for multiple commands

Let's say I want to execute several commands with similar flags such as: du -sh / --exclude=/dir1 --exclude=/dir2 --exclude=/dir3/dir4 tar cvf archive / --exclude=dir1 --exclude=dir2 ...
3
votes
1answer
64 views

Run wc and display only the word count

I have been trying to create a file called ~/dictwords.txt, which contains the number of words found in the file /usr/share/dict/words. I already created the file then I removed it because I did it ...
5
votes
4answers
142 views

Help with “/usr/bin/stat: Argument list too long” error

I need to get the list of files(.log/.lst) present in a directory($logfolder) whose creation date is in a specific $year and $month stat --format='%y %n' $logfolder/* | grep "$year-$month-"| ...
8
votes
2answers
344 views

disable CTRL-D window close in terminator (terminal emulator)

I am often logged in through multiple SSH sessions. To logout from my sessions, I press CTRL+d, until I am back on my local machine. However, sometimes I press once too many, and my terminal exits. ...
4
votes
1answer
77 views

Launch background processes in one group and later kill them all

The other day I tried writing a script that would kill a PID and all its children processes, but after spending some time on it, I decided it wasn't trustworthy, because sometimes some of the children ...
7
votes
6answers
723 views

How to read first and last line from cat output?

I have text file. Task - get first and last line from file after $ cat file | grep -E "1|2|3|4" | commandtoprint $ cat file 1 2 3 4 5 Need this without cat output (only 1 and 5). ~$ cat file | ...
0
votes
2answers
32 views

list files and store it in variables

im new with shell programming. my goal is to give the user a selection which file should be run. i catch all available scripts in one var with: var=$(find script*) so far so good.. this is the ...
1
vote
2answers
37 views

How to get text at start up of terminal

How to get text at start up of terminal as shown in this image.It should show whenever i open terminal.
6
votes
1answer
52 views

How do I use colors in the MOTD?

I edited the default /etc/update-motd.d/00-header, adding some color to make it easier to read: printf "Welcome to \e[1;34m%s\e[0m \e[2m(%s %s %s)\e[0m\n" "$DISTRIB_DESCRIPTION" "$(uname -o)" ...
2
votes
1answer
49 views

How to simulate user interaction when running another script

I am new to shell scripting. When I want to run a bunch of Linux commands I do fine, but how do I give user input when another script is called and asks for input while it runs. Here is the situation ...
5
votes
2answers
172 views

if statement in .bashrc not working correctly

I set up .bashrc to show a long prompt if the terminal is at least 80 characters wide. Otherwise it shows a degraded, smaller prompt. I use an if statement to achieve this: dp_smaller_than=80 if [ ...
2
votes
4answers
119 views

How to initialize an array using awk and bash?

I am trying to store values of the first line of a text file into an array. Here is what I have so far: arr_values=() awk ' NR==1 { for (i=0; i<=NF; i++) ...
5
votes
3answers
315 views

Is there any harm in using variables that aren't set?

Say I have the following code: # Check if the color prompt is enabled and supported on this system if [ -n "$force_color_prompt" ] && [ -x /usr/bin/tput ] && tput setaf 1 ...
7
votes
2answers
221 views

Cannot sum numbers received from stdin using bc

I'm trying to calculate the average entropy of files contained in a folder using: { echo '('; find . -type f -exec entropy {} \; | grep -Eo '[0-9.]+$' | sed -r 's/$/+/g'; echo '0)/'; find . -type f | ...
1
vote
3answers
36 views

How to run executable program with filter

I want to run a shell script. This script have a long name. So I want to use filter for file. ex: ls | grep myfile | ./ Is it possible to execute a file with filter.
1
vote
2answers
30 views

Start several fish shells in different directories?

In order to be able to launch my work environment with a single command, I want to start several urxvt windows running fish shell in different folders. However, I found no obvious way of having fish ...
1
vote
1answer
30 views

Kill all queued jobs

I need to kill all the queued and running jobs on my ID. I have tried at -l | awk '{print $1}'| at -r {} But I keep getting {} does not exist Which leads me to believe that I am parsing ...
5
votes
1answer
69 views

Why does `bash -c somecommand` sometimes not leave a bash process?

On an Ubuntu 12.04, with GNU bash, version 4.2.25(1)-release (x86_64-pc-linux-gnu), I tried the following command: $ bash -c 'pstree -s $$' init───sshd───sshd───sshd───bash───pstree $ bash -c 'pstree ...
6
votes
3answers
59 views

Can we configure different shells for different users on a single Linux/Unix distribution?

Well, this is not something that I want to do but I ask this question to know more about Shell configuration in Unix/Linux systems. So, the situation that I want an answer to is the following -: As ...
-16
votes
3answers
122 views

Which amongst the given option is TRUE about login shell?

Which amongst the given option is TRUE about the login shell? The login shell varies every time the user logs in. The kernel decides on the availability of the shell during login. The login shell ...
0
votes
1answer
72 views

Bash Script : Passing a variable to a bash script that contains quotes, single quotes. etc [closed]

lets assume this is the string: 'a',"b" it contains both single and double quotes. how would you pass this to a bash script as a single string ? this is the bash script: #!/bin/bash echo $1 ...
2
votes
2answers
99 views

“cat” command: how to automatically escape everything that might be a violation?

If you copy the contents of httpd.conf and then paste it into a cat command.. such as this one.. #!/bin/bash cat > /test << EOF pasted here.. EOF you run into this error: -bash: ...
0
votes
2answers
47 views

How do I sort using the grep and sort command

I would like to create a sorted list of all TCP services found in the file /etc/services. Pipe the output of the command grep tcp /etc/services into the command sort. Redirect the output of this pipe ...
2
votes
3answers
60 views

Can I chain pgrep with kill?

I have noticed that | is used to send results of first command to the another. I would like to kill all processes that match a name. This is what pgrep normally does: $ pgrep name 5089 5105 And ...
1
vote
5answers
46 views

grep for text that may or may not be present

Lets say I have a file batman; robin; superman; password = ""; wonderwoman green lantern if I want to check if there is a password present, i.e there is something entered in the "" . here is an ...
1
vote
1answer
29 views

Assign diff -y column names

I have two files and a shell script. File 1: Batman Superman John Snow Jack Sparrow Rob Stark File 2: Batman Ironman Superman Spiderman John Snow Arya Stark Jack Sparrow Rob Stark The hound ...
-2
votes
5answers
65 views

Resources to learn shell scripting [closed]

I have been using GNU/Linux for sometime now (Ubuntu and Fedora) and now I am trying to learn shell scripting from scratch. I would really appreciate if someone can guide me on choosing right ...
0
votes
2answers
97 views

Running system bash command in PHP script - syntax error: unexpected T_LNUMBER

If anyone can shed some light on my issue that'd be great. Please don't down-vote me; I'm new to the language and the OS itself and I'm trying my best to research before asking questions, so any ...
1
vote
1answer
44 views

Awk that I am stuck on

I have a project I am working on for work. The script I am building initially takes two arguments: one is an unique Identifier and the other is for a log file (both strings). Now I have the first part ...
3
votes
4answers
155 views

How to cut everthing until a specific word / after a find in a script

Hello I try to get the output of files from today wich contains ERROR. I use this to find the files I want: find /home/user/logfilesError/ -maxdepth 1 -type f -name "gandalf_*"\ -daystart -mtime ...
0
votes
3answers
25 views

Finding and replacing text inside awk block

I want to find and replace a value inside awk block. Here is a sample input file to my script P1 10,9:11/18013013582 ,10:1 ,167:0 ,487:5/E.164 11,9:15/310410532169026 ,10:60 ,167:0 ,487:4/IMSI ...
2
votes
1answer
488 views

bottomless tee?

I was just playing around in the terminal and I did this: printf 'some string\n' | { tee /dev/fd/3 | { : && sed 's/some/string/' } } 3>&0 I was really surprised when ...
7
votes
3answers
167 views

Local, timestamped logging of all ssh commands?

How can I keep a local, timestamped record of all remote commands I use in ssh (command-line openssh client started through bash)? Requirements: Essential: 100% client-side without relying on ...
1
vote
3answers
420 views

Difference between ls -l and ll?

I'm relatively new to programming as a whole and some tutorials have been telling me to use ls -l to look at files in a directory and others have been saying ll. I know that ls is a short list, but ...
3
votes
1answer
98 views

Rename files with spaces in a BusyBox shell

I'm trying to rename some files on my Synology Diskstation via SSH. The available shell is the BusyBox built-in shell: BusyBox v1.16.1 (2013-04-16 20:13:10 CST) built-in shell (ash) The move ...
6
votes
2answers
348 views

Array in unix Bourne Shell

I am trying to implement array in Bourne shell (/bin/sh). I found that way to initialize array elements is: arr=(1 2 3) But it is encountering an error: syntax error at line 8: `arr=' unexpected ...
0
votes
1answer
117 views

How do I cat a command file?

I have the output of the crontab -l stored in a file (crontab_file) with no extension. But whenever I try to cat it, I get errors saying command not found for multiple line of the file. Here is the ...
3
votes
2answers
66 views

Gzip large amount of symlinked files

I have a folder containing a large amount of symlinked files. These files are each on the order of 10-11GB (fastq files to be specific). They come from a variety of source folders, but I made sure ...