Questions specific to GNU’s Bourne Again SHell, as opposed to other Bourne/POSIX shells. For questions about Unix shells in general, use the /shell tag instead.

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1
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4answers
429 views

is there some simple/clean way to make an “empty boolean variable” be evaluated as `false` on bash scripts?

Well, the variable is not boolean until it has been set to true or false. So when the script begins, it checks for a boolean that was not set yet as in bTest=''. So if I do this: if $bTest;then echo "...
0
votes
1answer
699 views

perl one liners + print line if match last word but with space

The following perl syntax will print the line in case line was ended with "DUPLEX" But Sometimes DUPLEX have one space or more as "DUPLEX " so in this case line will not printed Please ...
3
votes
1answer
651 views

Using shell's read command with live editing functionality (readline like)

Is there a standard (POSIX) way of asking the user some data from within a shell script, with read for example, while allowing live edition of the text being typed (what readline does)? I know bash ...
1
vote
4answers
4k views

How to add an alias without directly editing the `bash_aliases` file?

Is there a way to add an alias from the command line without directly editing the bash_aliases file? To clarify, how can I make a bash script do it without having to enter something along the lines of ...
2
votes
5answers
2k views

How can I delete input in the terminal?

Xubuntu 13.10 Say I paste a command, something like sudo apt-get install abc yxz 123 DEF MMM KKK into the terminal. Then I suddenly had a change in mind and thus I would like to delete the last 3 ...
1
vote
5answers
949 views

Is there a way to make a Bash script enter a certain keystroke?

Is there any way to make a bash script enter a certain keystroke? What I'm trying to accomplish here is a script that will run Ctrl+B to exit tmux. EDIT: I see that several people are saying that it'...
8
votes
1answer
6k views

How to strip color codes out of stdout and pipe to file and stdout

I have a program that uses printf with some tput mixed in it and I'd like to pipe the output to stdout as well as a file. I'd prefer to use sed since I don't want any unnecessary dependencies on my ...
3
votes
1answer
2k views

cat file to udp, pt 2: send 1 udp packet per ^C-delimited line

Yesterday I asked a question about catting a file over a UDP socket in bash. The solution we came up was netcat -c -w 1 -v -u -s 127.0.0.1 239.255.0.1 30001 < test.txt. This worked in the sense ...
2
votes
2answers
973 views

delete directory with special character in filename

I have these tricky directories that I can't figure out how to delete. If I run ls -ld * I get… drwxrwxr-x 7 user1 taskfmri 2048 Jan 22 15:26 857263 drwxrwx--- 4 user2 ...
2
votes
2answers
1k views

Extracting parts of filename

I'm trying to use a part of the file name to be inserted into a new file created using the script. For eg: dcn_2014_01_31_14_17_45_505.pcap and dcn_2014_01_31_14_32_27_656.pcap should give ...
3
votes
4answers
13k views

Regular expression in Bash to validate IP-address

In my Python script i have a regular expression for searching IP-addresses like 0.0.0.0-255.255.255.255 in a file, it looks like this: [1-2]{0,1}[0-9]{0,1}[0-9]{1}\.[1-2]{0,1}[0-9]{0,1}[0-9]{1}\.[1-2]...
4
votes
4answers
1k views

Keeping the number of files in the folder constant by deleting old files

I'm trying to create a script and run it in crontab every 5 min, so that the number of files in a folder always remain 50000. If there are more, I want the script to delete the old files. #!/bin/...
2
votes
4answers
149 views

How to get started with bash? [closed]

I need a way to be able to run a script that will automate terminal commands, one after another. As I understand it, this is exactly what bash does. (Am I right, even on this count?) Where can I ...
0
votes
1answer
3k views

How I append the data of Multiple files into one file?

I want to append data of approx 500 files into one file and each of these files are located in their respective dirs. Also How i can verify the contents of merged file e.g How i verify that data ...
1
vote
1answer
192 views

$@ and 'set env $PATH' - Why should this statement go into .inputrc?

I have a line in my .zshrc that says: set env $PATH Apparently this affects the value of $@. I have read that $@ should be empty and that I should not have any set statements in my .zshrc (at least ...
0
votes
1answer
321 views

Preventing a new instance of a program to open when calling it

My problem is with FBI (frame buffer image viewer) for Linux, but my question and any answers are perhaps applicable to more than only that program. I don't know. Anyway… While things are loading on ...
0
votes
2answers
151 views

Deleting large number of files

I'm writing a script to delete large number of files in linux. The script will run every two minutes in crontab. I tried using the find /mnt/md0/capture/DCN/ -maxdepth 1 -type f -name "*.pcap" -...
5
votes
1answer
2k views

ls -l --group-directories-first (act on symlinks as well)

ls option --group-directories-first causes directories to be listed on the top, which makes the output of ls nice and clean: ls -l --group-directories-first However, it does not act on symlinks, ...
2
votes
2answers
332 views

How to split files with common prefix in bash

I have a directory with many files with common prefix, like gsc*_other.foo, where * is a character that goes from 0 to 9 or a/b (where a stands for 10 and b for 11). My goal is to create text files ...
9
votes
1answer
189 views

colorize bash_completion

When I type grep and then press TAB twice, bash_completion will list files and directories in current directory. It will also complete filenames when I type initial letter. That is all very nice, the ...
4
votes
2answers
20k views

Mysql query resultset in bash script

I am using the bash script to connect to the mysql database and execute a query. I use the below script to connect to the database and execute the query. #!/bin/bash Total_Results=$(mysql -h ...
1
vote
2answers
4k 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
307 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 ...
19
votes
8answers
17k 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
139 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
1k 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
7k 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
651 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 #!/bin/...
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 10.1....
2
votes
2answers
114 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
435 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
292 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
980 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
728 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
180 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
4k 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
303 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
6k 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
4k 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 ...
3
votes
1answer
8k 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
113 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 /media/usama/CRUNCH/...
19
votes
2answers
6k 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 ...
2
votes
1answer
187 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
274 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
797 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
579 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 ...