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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1
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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 ...
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 ...
4
votes
2answers
125 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", ...
9
votes
2answers
243 views

How a piped shell programs balance their output/input rates? [duplicate]

Possible Duplicate: Bash while loop and reading from pipe I come from web programming background, and find myself interested in one peculiarity of using a local shell. I understand that ...
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
38 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 ...
5
votes
3answers
301 views

How to cd automatically after git clone?

I want to automatically cd to the directory created by the clone command after I git cloned something. Shell: ZSH if that matters.
4
votes
3answers
90 views

Transactional UNIX shell for file system changes

It is easy to make a mistake when copying (cp), moving/renaming (mv), removing (rm/rmdir), creating dirs (mkdir), and changing file permissions (chmod). It would be nice to have a log to view before ...
0
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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 ...
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. ...
0
votes
1answer
597 views

Converting update-rc.d redis_6379 defaults to chkconfig command

I'm trying to run the commmand below to Centos and of course I get command not found. How do I then convert it to chkconfig ? update-rc.d redis_6379 defaults
2
votes
1answer
276 views

ctrl c vs. ctrl z with foreground job

Ctrl+Z stops the job whereas Ctrl+C kills the job. Why is that? Wouldn't the other way make more sense? z@z-lap:~$ sleep 100& [1] 4458 z@z-lap:~$ sleep 200& [2] 4459 z@z-lap:~$ jobs [1]- ...
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 ...
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 ...
2
votes
1answer
383 views

KSH styling text based menu using STDERR

Is it possible to format the STDERR in order to have a better looking menu using the select command? I have a simple select select oChoice in $(<tempMenu.menu) ; do case "$oChoice" in ...
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 ...
7
votes
6answers
722 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
1answer
51 views

ksh, perform action when reaching loop maximal value

I am looking to write a small korn shell script doing 5 tests (by waiting some time before each one) and then, if they all fail, performing an action. I was looking at doing something like : for ...
3
votes
1answer
41 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 ...
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 ...
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 ...
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 ...
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)" ...
3
votes
3answers
2k views

Check whether files in a file list exist in a certain directory

The runtime arguments are as follows: $1 is the path to the file containing the list of files $2 is the path to the directory containing the files What I want to do is check that each file listed in ...
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.
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-"| ...
21
votes
4answers
1k views

Is the shell permitted to optimize out useless terminating commands?

If a shell is asked to perform a probably useless (or partially useless) command known to terminate, such as cat hugeregularfile.txt > /dev/null, can it skip that command's execution (or execute a ...
19
votes
4answers
1k 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 ...
12
votes
1answer
265 views

Percent in $PATH environment variable

My $PATH looks like this: ...
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 ...
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
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
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 ...
2
votes
4answers
121 views

How do I pass a variable from my local server to a remote server?

I am trying to pass a variable from my local server (location1) to a remote server (location2). The purpose of the code is to copy a file from the remote server from a predefined location. In simpler ...
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.
2
votes
5answers
73 views

How to copy 5 newest files from one directory to another and delete the old copies

How can I copy the 5 newest files from a directory to another in a "new to old" order.
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++) ...
2
votes
2answers
303 views

See extended attributes with coreutils ls on Mac

I have coreutils installed via MacPorts on my Mac running OS X 10.8.4. I have ls set to use the coreutils version of ls [(GNU coreutils) 8.21] when available: if [ -e /opt/local/libexec/gnubin ]; ...
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 | ...
0
votes
1answer
467 views

Why alias does not work in AIX (korn shell, .profile)?

I have these files in my home directory: drwxr-xr-x 3 meuser staff 256 Oct 12 13:11 . drwxr-xr-x 102 bin bin 4096 Sep 30 12:28 .. -rw------- 1 meuser staff ...
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
4answers
166 views

Write program output to log file containing PID in its name

How can I start a program and write its output to a log file, where the log file contains the PID in its name? I tried program_a > log_$! which doesn't work since $! is the PID of the last ...
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 ...
26
votes
4answers
3k views

What is the correct name for the “>” command

I was trying to find how to pass some text to a file without overwriting what's there already using the > command and I realised I don't know what it's called. Searching for right arrow or right ...
9
votes
3answers
6k views

How to see how many context switches a process makes?

I want to see if my process makes a lot of context switches. I also want to see how manpulating task groups affects the number of context switches.
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 ...
-11
votes
2answers
162 views

Count the number of executable programs in a directory [closed]

How can I count the number of executable regular files in the current directory in a shell script?
0
votes
1answer
71 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: ...