Questions about bash only, as opposed to other Bourne/POSIX shells. For all Bourne/POSIX-style shells, use the /shell tag instead.

learn more… | top users | synonyms

1
vote
2answers
3k views

How do I run two ongoing processes at once in linux/bash?

I would like to know how I can run two ongoing processes at the same time in Linux/bash. basically, I have a Node web server, and a MJPG-Streamer server. I want to run both these processes at once, ...
2
votes
2answers
263 views

How do I share stdout between multiple processes?

I want to receive live TCP stream, and make it readable by another processes at the same time, without saving it. For example, 111.222.233.244:1234 streams actual time. Server supports only one ...
14
votes
7answers
12k views

bash: test if $WORD is in set

I am looking for a construct in bash, to decide if a variable $WORD is one of defined words. I need something like this: if "$WORD" in dog cat horse ; then echo yes else echo no fi does ...
17
votes
2answers
1k views

replacing backtick with $() not working

I have some old scripts that I try to update. Some of the code condenses to: export X=`(echo "abc"; echo "def")` echo $X which gives the expected output: abc def Now the internet tells me ...
3
votes
2answers
137 views

Customizing bash for many servers

I work with a few dozen servers. I'd really like to streamline my work, but at the same time I'm a bit reluctant, since it would be a lot of work synchronizing all servers. The servers are in ...
2
votes
2answers
458 views

Zenity refuses to work in background

I'm trying to create a background bash script which creates a popup in certain circumstances, however, my code only works when run manually in a terminal (e.g. not in the background). I've tried ...
12
votes
3answers
6k views

How to redirect the output of any command?

I'm trying to write a simple script to monitor my network status, without all of ping's output: ping -q -c 1 google.com > /dev/null && echo online || echo offline The problem is that ...
1
vote
2answers
569 views

Neither crontab nor anacron is running, how to debug?

I'm running Arch ARM on a PogoPlug and want to execute a file every hour, the file when call directly runs fine (it is executable), for testing the file /etc/cron.hourly/crontest contains ...
5
votes
7answers
2k views

Replace a character except last x occurences

I have a file that has a bunch of hostnames correlated with IPs that looks like this: x-cluster-front-1 192.168.1.2 x-cluster-front-2 192.158.1.10 y-cluster-back-1 10.1.11.99 y-cluster-back-2 ...
2
votes
2answers
110 views

Using Sed with Regex

I would need to edit the values in a file delimited by colons (:) I would like to replace the contents of the file by using regular expression. After a grep to confirm that the item exist in the file ...
1
vote
1answer
339 views

using grep --perl-regexp

this is a sample output of ls $ ls -lAF -rw------- 1 martin martin 168 Jan 25 23:26 aaa -rw------- 1 martin martin 168 Jan 25 23:26 bbb -rw------- 1 martin martin 168 Jan 25 23:26 ccc I would ...
0
votes
3answers
239 views

Convert Country List to Continent List in Bash

I am doing some geoip lookups using the geoiplookup command in Linux. This correctly returns the country codes for me but I need to break them down into continents instead of countries. I currently ...
0
votes
2answers
867 views

Is CDPATH behavior broken in bourne shell (/bin/sh)

I have the following script: #!/bin/sh mkdir -p /tmp/test/foo cd /tmp/test unset CDPATH echo "TEST1: Current working directory: ${PWD}" echo "TEST1: attempting to 'cd foo'" cd foo echo "TEST1: ...
4
votes
1answer
596 views

How to execute a Bash comand and execute two statements on failure?

Ì want to execute a Bash command, followed by two actions if and only if the test returns an error. I would prefer to solve this task as a one-liner in Bash. Here are the two forms I have tried: ...
1
vote
1answer
167 views

Bash Array does not store correctly

I have a problem with my bash array I was trying to read the file however the array allocated it in array[1] instead of 0 #!/bin/bash index=0 INPUT=BookDB.txt OLDIFS=$IFS IFS=: i=0 book=() [ ! -f ...
4
votes
5answers
3k views

Bash Script to Sort Files into Alphabetical Folders on ReadyNAS Duo v1

I have an old ReadyNAS Duo v1 (Sparc) running an unknown flavour of Linux. I have a folder structure with 1,000+ files I want to move into a folder structure based on the first letter of the file ...
6
votes
5answers
3k views

How does one find out how many bits a file has in one command?

I know I can use ls -lat to find out how many bytes has a file and then multiply by 8 to find out how many bits. But is this possible in only one command line?
2
votes
3answers
218 views

how to prevent alias expansion by `eval` to an arbitrary alias, and keep the endless loop protection on a function?

IMPORTANT: do not use eval! (I learned this later..) In a function, eval expands sleep to its alias, so I prevent the endless loop this way: function FUNCexecEcho() { echo "EXEC: $@"; shopt -u ...
1
vote
1answer
5k views

Meaning of `export PATH=…` in .bash_profile

I'm using a mac for some years now and as I'm currently learning ruby on rails, I felt like I should learn more about the system I'm using. I took a look at the ~/.bash_profile, it looks like this ...
5
votes
0answers
1k views

Changing HISTTIMEFORMAT leaves entries with incorrect date [duplicate]

After exporting HISTTIMEFORMAT='%F %T' I tried to query history But the result shows all the commands are executed on same day. How can I check the actual date and time of actual command execution?
4
votes
2answers
3k views

Find files newer than another file within each subdirectory

I have a folder structure like this /Class/Student/Unit/files Each Unit folder contains a file MarkSheet* that I update when I mark a students work. I need a script that tests if the student has ...
2
votes
1answer
6k views

Using bash “&” operator with “;” delineator? [duplicate]

I'm trying to write a command that's a one-line for loop containing a command that uses the & operator to put the command in the background: for dir in $(ls); do command $dir &; done Where ...
3
votes
2answers
108 views

Trimming Filenames from the end

I have a folder with following mp4 file which are needed to be renamed for filename in /media/usama/CRUNCH/RO_Plant/RO_Videos/*; do File1=$filename echo $File1 done ...
17
votes
2answers
5k views

What is the difference between “du -sh *” and “du -sh ./*”?

The title says it all. What's the difference between those 2 commands? NOTE: I'm more interested in the * and ./* part.
-1
votes
1answer
1k views

How to print gmail inbox messages

I want to print inbox messages one by one (like cat someFile) so that I can parse the message contents. something like printGmail InboxMesg1 | grep some | sed some Using curl I can access the ...
1
vote
1answer
166 views

Bash: show prompts if arguments weren't provided

What is the best way of supporting in the script prompts and arguments at the same time? I want to show prompts if arguments weren't provided. Is there something better/shorter than this? ⇩ ...
2
votes
3answers
238 views

Bash: change variable defined at top of script

At the top of my script I have some variables defined like so # Start Variables defaultmap="de_dust2" port="27015" sourcetvport="27020" clientport="27005" maxplayers="16" ip="0.0.0.0" parms="-game ...
6
votes
1answer
672 views

Bash is automatically reloading (injecting) updates into a running script upon saving it: Why? Any practical use?

I was writing a bash script, and happened to updated the code (saved the script file to disk) while the script was waiting for some input in a while loop. After I returned to the terminal and ...
5
votes
5answers
523 views

A shell script to write selected fields to a single line

I have a log file trace.log which prints the time stamp, thread name and Transaction method and transaction ID as below. 2014-01-23 15:50:41,724 [catalina-exec-35] INFO TRANSACTION getConnection ...
2
votes
1answer
456 views

arrow keys are not working with terminal server telnet (termnetd) session

I am using terminal server package termnetd 3.2, which reads serial port and gives output on telnet port. I logged into terminal server port, every thing works fine except the arrow keys, Home and End ...
22
votes
3answers
31k views

“su” with error “X11 connection rejected because of wrong authentication”

As root, I'm connecting to a remote host to execute a command. Only "standarduser" has the appropriate id-file and correct .ssh/config, so I'm switching the user first: su standarduser -c 'ssh -x ...
2
votes
1answer
384 views

kill process in script while writing file behavior

in my php script which runs as a cron job, I have foreach($sites as $site) { exec('./wkhtmltoimage-amd64 ' . $site . ' somefile.png'); exec('./zopflipng -y somefile.png somefile.png'); } ...
1
vote
2answers
515 views

Why mkdir -p /Local/Foo/Bar/Wah not work but cd /Local and mkdir -p Foo/Bar/Wah works? [closed]

I am trying to create a local folder in my local development machine, on Mac OS X Mountain Lion, so I did: sudo mkdir /Local sudo chmod 777 /Local mkdir -p /Local/Foo/Bar/Wah (note that last line ...
3
votes
1answer
1k views

Bash autocompletion for an environment variable holding a directory name

I'm using, among other things, bash 4.2.37 on Linux Mint 14. When I autocomplete the name of an environment variable by typing Tab, it expands to the name of the variable followed by a space. If the ...
4
votes
1answer
53 views

How to read value of variable, where the name of variable is the value of another variable

I think an example is in order. Consider I have these two environment variables setup (by a Continuous Delivery tool): PACKAGE_VER=1.2.3 and USE_VERSION_FROM=PACKAGE_VER. What I want now is a script ...
1
vote
1answer
786 views

How to copy files within a remote server?

I would like to copy files in an remote server from one directory (in the remote server) to another (also in the same remote server). I tried this: scp -r myacc@remote.server:/folder_a/*myfiles* ...
1
vote
2answers
212 views

processor(s) statistics that is one day old

I already know how to use grep -w cpu /proc/stat in order to get the cpu stats and identify the user mode. Percentage wise, I just divide it my the total time from the /proc/uptime. However, how can ...
2
votes
1answer
3k views

The amount of time since the system was last booted [duplicate]

I have used both uptime and cat /proc/uptime commands. I know the idle time in the later can be greater than running time (multiprocessors). However, when I add both running and idle times, and ...
2
votes
2answers
930 views

Keeping xterm terminal alive on crunchbang linux debian wheezy

I like to keep a number of terminals open at different locations on my development VM. For this I use terminator because I got a big screen and I can divide the terminals anyway I want. But after ...
1
vote
3answers
5k views

Remove whitespace and parentheses in filenames with sed [duplicate]

I'm an absolute newbie in the unix area so forgive me off the bat if I've gone about this the wrong way. I have a series of files I need to rename which all have the pattern " (*)" in them. Eg; ...
1
vote
1answer
48 views

Where can I find documentation on shell script syntax for using a regex within a variable construct?

I'm debugging a shell script (which I didn't write) that contains this loop: read line < "$pid_file" for p in $line ; do [ -z "${p//[0-9]/}" -a -d "/proc/$p" ] && pid="$pid $p" done ...
1
vote
4answers
520 views

How to start line with command from output of another command

Sometimes the output of some command include other commands. And I'd like to start that command from output without using a mouse. For example, when command is not installed there is a message with ...
0
votes
1answer
275 views

Shell spawned backgrounded process is still hanging [closed]

It seems processes spawned after || make the parent shell hang with them. For example, do in your terminal $ cat <<"EOF" >/tmp/hello_im_still_here #!/usr/bin/env bash killall emacsclient ...
2
votes
3answers
96 views

How to start first command from the list printed by command 'history | grep something'

For example, I have the following output from command: loom@loom:$ history | grep MAKE 219 ../build.sh -DCMAKE_BUILD_TYPE=Debug .. 909 history | grep MAKE How to write a command, that start ...
3
votes
2answers
382 views

How do you preserve a space in a literal expression in an array value in bash and how to trim down results from a sort command?

In the context of searching for expressions in log files, I was wondering generally if there was a way to quantify and qualify the contents of the logs in /var/log in some way. In particular, does the ...
0
votes
2answers
101 views

Configuration file for Virtual Console

Does any configuration file exist for virtual console, when a user logins in it which is read and executed ? My requirement: To execute some shell commands when a user logins using the virtual ...
6
votes
5answers
2k views

Using a generated list of filenames as argument list — with spaces

I'm trying to invoke a script with a list of filenames collected by find. Nothing special, just someting like this: $ myscript `find . -name something.txt` The problem is that some of the pathnames ...
2
votes
2answers
662 views

How to asynchronously launch external program from cli and discard its output?

I'm writing a simple desktop initiation script which waits for disk idle, and then launches next external program (like Firefox, Skype or conky) using &, like: ps cax | grep conky > /dev/null ...
3
votes
3answers
2k views

Bash Script To Find Debian Release Number from /etc/debian_version

The following is what I'm currently using for testing the version of Debian. Instead of doing it this way, can I make it more succinct? #!/bin/bash VERSION=NONE if [ $(cat /etc/debian_version) == ...
3
votes
1answer
180 views

Can someone clarify this Bash script

I'm learning something about Bash scripting, and I came across this example: The task is to write a Bash script that reads a file, given with the first argument, pulls out those records that have the ...