Questions about shell scripts, executable files that are interpreted by a shell (bash, zsh, etc.).

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4
votes
4answers
12k views

Check for Process if Same is Running

Is there a script or a way in linux that when I try to execute a shell script/process, if the same is running, it will prompt that same is running and will exit otherwise it will continue.
-3
votes
2answers
7k views

how to execute a python program in a shell script

I have a python program in that I wrote some python code (disk.py). I executed this program using the command python disk.py in a terminal, it worked. Now I want to execute it using a shell script.
0
votes
1answer
323 views

Capture Error of LS to file [duplicate]

#!/bin/sh if [ $(ls sample01.log | wc -l) = 1 ] then echo "File Found" > lsOutput.log else echo "File Not Found" > lsOutput.log fi But if sample01.log is not already existing my code already ...
4
votes
1answer
186 views

measure amount of data read from /dev/random

background I have written a collection of bash scripts (most of them in German only yet but if you are interested; download the archive not the single scripts) which help users create high-quality ...
6
votes
3answers
14k views

Adding a Column of values in a tab delimited file

How can I add a Column of values in a file which has a certain number of rows. I have a input file like this: Input file: SPATA17 1 217947738 LYPLAL1 1 219383905 FAM47E 4 77192838 SHROOM3 4 ...
2
votes
1answer
465 views

bash script - need date command variable

I am trying to create a script that will parse the /var/log/secure file for failed login attempts for today's date only and redirect those attempts into a separate file so I can view those attempts ...
2
votes
5answers
397 views

Replace instance of process in place?

I suspect this is not doable just because of the security implications, but here's what I'd like to do. Basically we run a bash shell-script on our CentOS server that calls Program-A (in our case ...
1
vote
3answers
658 views

What does “FILENAME=$(echo $INFILE | grep -oE ”[^/]+$“) ” mean?

FILENAME=$(echo /root/Source/code/script.sh | grep -oE "[^/]+$") I know that it would give me the file name from the file path here as script.sh. But can some one please explain me this?
0
votes
1answer
704 views

How to write simple if condition in ash?

I would like to write a small script that would check every once in a while if I have the internet connection. I would like to run it in crontab on my router where I have ash. I am having a hard ...
0
votes
2answers
34 views

Shell script to format logs

Requirement : I need to write a script to find out for which API the request has been sent but no response received. Given below is an example of the logs i'll be working with. 2014-02-28 ...
2
votes
2answers
296 views

Bash script to signal a concurrently running instance (same script) about a condition and increment counter

Background Here's what I want to achieve. I have a (potentially) long-running process. Now I have locking in place just fine and all is generally in order. However, since this is a scheduled job, ...
1
vote
1answer
92 views

What is the Command to check the history of the command executed which should based on the user who accessed it [closed]

I am looking for the command or script to meet the following requirement. I wanted a history of all the users who connected to my machine and what commands they execute in there session and at which ...
3
votes
5answers
1k views

Quoting and escaping

I have a shell script, the arguments of which are collected in quote as a single argument and passed to a perl script. /usr/local/API/check_api.sh "-D x.x.x.x -C Test_Internal_Cluster -u user -p pass ...
3
votes
2answers
8k views

bash script error: source: not found

I must be missing a fundamental understanding about sourcing files in bash. I've tried the different approaches that seem like they should work, but I still get this error source: not found. In my ...
2
votes
3answers
109 views

How to optimize this oneliner? (if second column empty, put the line in another file)

I have a little "oneliner": while read ONELINE; do if [[ -n "`echo $ONELINE | awk '{print $2}'`" ]]; then echo "$ONELINE" >> LIST-ok.txt else echo "$ONELINE" >> ...
7
votes
7answers
3k views

How to detect the desktop environment in a bash script?

I am writing a bash script that needs to know which desktop environment (XFCE, Unity, KDE, LXDE, Mate, Cinnamon, GNOME2, GNOME3,... ) is running. How can I obtain that information?
1
vote
0answers
55 views

manipulate a Drush “internal” variable

I want to modify a variable (preferably in a Bash Script format) because my PHP environment requires a port number. To show a URL in Drush containing a token that logs you in as user 1 (without a ...
-1
votes
1answer
50 views

growing up with linux scripting and online resource to learn it [closed]

Is learning Linux shell scripting good for developing own career?I use linux and very much interested in scripting. Where should I start from?
0
votes
1answer
70 views

Is it a bad idea to keep scripts in /root? [closed]

Is it a bad idea to keep scripts in /root? Simple bash scripts that have the following permissions: -rw-r--r-- They execute fine when ran as root, but is this bad practice? It's a multi-user system, ...
2
votes
2answers
2k views

Read non-bash variables from a file into bash script

My bash script needs to read the variables from a text file that contains hundreds of variables, most of which conform to standard bash variable sytax (e.g., VAR1=VALUE1). However, a few lines in this ...
3
votes
2answers
479 views

Moving large numbers of files and directories to a different directory

I'm trying to move the following move a large number of files that exist in the following structure to a /mnt/originals but I need to maintain the structure at the same time. I know cp would be a ...
6
votes
3answers
5k views

reliable return code of background process

Let's assume the following piece of bash code: foo > logfile 2>&1 & foo_pid=$! while ps -p$foo_pid do ping -c 1 localhost done wait $foo_pid if [[ $? == 0 ]] then echo "foo ...
3
votes
2answers
3k views

Interactively concatenate video files

Problem : How to concatenate (join) multiple MP4 video files into one file interactively? There are a lot of programs that do this for two files from the command line. For instance : ffmpeg, ...
-1
votes
2answers
4k views

Cron job is not working [closed]

i have a cron job center code hereonfigured at var/spool/cron/testuser, Am calling "adindex.sh" file from there. Am getting results when am directly put the command directly in prompt(php and sh), ...
0
votes
1answer
170 views

Combining two bash scripts by adding flags

I have two scripts which transform the code from software v.1 to software v.2 and viceversa. These are essentially a lot of sed substitutions. In the way I wrote them they accept two arguments: ...
2
votes
4answers
3k views

move file by list in file

I have a file the contain filenames, for example: /tmp/list.txt (it is with the spaces at the start of each line): /tmp/file.log /app/nir/home.txt /etc/config.cust I want, using one line, ...
4
votes
3answers
234 views

shell script problem with using the operators

I am comparing two strings using the levenshtein distance algorithm. I got the PHP implementation of the algorithm from here. I am calling this php implementation from my shell script as below. ...
4
votes
2answers
343 views

Dump process's stdin and stdout

I have two processes, let's say Parent and Child. Parent launches the Child and communicates with it through child's stdin and stdout. Parent <-> Child These processes use text protocol and I ...
24
votes
3answers
11k views

If I sudo execute a Bash script file, will all commands inside the Bash script be executed as sudo as well?

I want to write an automated post-installation script in Bash (called post-install.sh, for instance). The script will automatically add and update repositories, install and update packages, edit ...
4
votes
2answers
675 views

Shell Script to isolate files scattered in different folders

I need to write a shell script that traverses a given directory structure in multiple levels, recognizes the video files scattered in the folders and copies all of them to another single folder. The ...
7
votes
1answer
456 views

Parallel execution of bash script

I have a table URL_Experiment in my database (mySQL database). I have 2 million URL links in this table. For each URL, I am checking if some particular text is present in the URL and updating the ...
1
vote
1answer
64 views

what is $# used in a script for? [duplicate]

In many scripts in my organisation and even on online tutorials, this is a common if clause I come across : if [ $# -eq "somethng" -o $# -eq "somethng" ] what does this $# condition ...
-4
votes
1answer
39 views

Implementation Logic [closed]

I have two files,which is something like this: file1 msgid "New" msgstr "" dsvhuvchvdhcvhc msgid "Old" msgstr "hsvhs" kdnvcjdbvj msgid "Bold" msgstr "" file2 dcbjdsbc msgid "New" msgstr "Alas" ...
3
votes
4answers
8k views

Bash script to convert all *flac to *.mp3 with FFmpeg?

I want to convert all *.flac to *.mp3 in the specific folder. This is what I've tried, but not works: # change to the home directory cd ~/music # convert all *.flac files ffmpeg -i *.flac -acodec ...
0
votes
1answer
51 views

Getting a delimiter issue while executing the script

I am creating a test.sh file and i am running it as ./test.sh: string="hello" ed << EOF e any_file 1i ${string} EOF can anybody help me what it does? I am getting some delimiter issue. Can ...
1
vote
2answers
77 views

How can I substitute one command for another temporarily?

I'd like to alias sed to gsed, but only while a particular script is running. I have a script that invokes sed. On the Mac, BSD sed doesn't support the required features, but I don't want to replace ...
0
votes
2answers
88 views

Increment Daily Config Value

I have a configuration file that contains a lookback value, which I need to increment by +1 each day. IE: 60, 61, 62 etc.... It doesn't look like awk will work because of the formatting of the ...
5
votes
1answer
480 views

counting multiple patterns in a single pass with grep?

I've written a grep loop to iteratively count DNA trinucleotides within a gzipped DNA fasta file containing DNA sequences e.g. declare -a tri=(AAA AAC AAG AAT CAA .. etc) for i in ${tri[@]} do ...
2
votes
1answer
115 views

Monitor setup commands do not work in script

I'm running Arch Linux 64-bit on a Samsung RV511. I often connect external monitors using xrandr. As I run LXDE with Awesome as a window manager, I need to prepare the xrandr-command by killing ...
0
votes
0answers
71 views

Shell script use ssh forwarding to send a file to a second system

I have ssh forwarding enabled and ssh to server A. On server A I want to run a script as root and take advantage of the ssh key being forwarded for USER to send a file to system B. I'm getting a ...
1
vote
1answer
129 views

print all values of a file after removing some characters using grep

I have a file in which the values are stored as below. Assistant Professor at SASTRA University St John's memorial college Paul George Univeristy Department Chair at University of Texas I am ...
2
votes
3answers
2k views

Extracting characters after a particular text

I am extracting a page from website using cURL command. curl "www.google.com" -s | w3m -dump -T text/html > foo.txt The w3m command outputs the HTML page in a much more simpler format so that ...
2
votes
1answer
427 views

shell script construct array for file elements

I have a file named input_file which contains some lines. I need to remove certain characters in the line and store them in an array. So to remove the characters, I use the sed command and storing in ...
0
votes
1answer
46 views

Using !n in script or interactive mode

I add to ~/.bashrc the following code: test_exclamation () { printf %s "$READLINE_LINE" | xargs echo } bind -x '"\eX": test_exclamation' I write to bash prompt buffer $ !1700 If I press Enter, ...
1
vote
2answers
145 views

Make Trickle get the correct $PATH

Trickle is a bandwidth limiting program. I have the following script for trickle. #!/bin/bash echo $PATH trickle -s -t 3 -u 200 -d 200 "$@" I have a script in ~/bin/ that want to run the script ...
2
votes
3answers
387 views

Copy command from history to bash prompt

Sometimes I'd like to get some command from history output, copy it to bash prompt, make some changes and run it. Is there a way to copy command from a history output to bash prompt without involving ...
1
vote
1answer
478 views

Basic script in Angstrom Linux running on a Beaglebone Black

On my embedded system, I can toggle a user led with: echo > 1 sys/class/leds/beaglebone:green:usr2/value. Similarly, I can find the value of a GPIO (gpio60) (set to input), with more ...
1
vote
3answers
314 views

Script to split string

@terdon's answer provides this script: find . -type f -name "*mp3" | while read file; do album="$(basename "$(dirname "$file")")"; filename="$(basename "$file")"; ...
2
votes
4answers
182 views

inline conditionals for assignment

Is there an "inline-equivalent" to expressions like the following?: if [[ $VERBOSE == 1 ]]; then V=$FOO else V= fi I'm thinking of something like this in perl, for example: $V = $VERBOSE ? ...
0
votes
3answers
2k views

“Expect” automation tool output to shell variable

#!/bin/bash # more commands here expect << EOD spawn telnet localhost 9151 expect -exact "Trying 127.0.0.1...\r Connected to localhost.\r Escape character is '^]'.\r" send -- "AUTHENTICATE ...