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

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2
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2answers
179 views

Shell Scripting: how to use part of the file path as the file name?

I have a group of directories, each containing exactly 1 jpeg image, like so- /psds/folder1/image.jpg /psds/someotherfolder/picture.jpg /psds/yetanotherfolder/thumbnail.jpg What is the appropriate ...
1
vote
1answer
446 views

Date calculation in script for notification alerts

I want to create account expiry alerts therefore I need to write a script which could alert me before 1 month of expiry over email. I'm working on Linux. I can get expiry information as 2015-27-03. ...
1
vote
1answer
1k views

Run smartctl on all disks of a server

My question is a quite simple , I want to run the command smartctl -i -A on all disks that the server have. Think that I've too much server with different number of disks and RAID Controllers, then I ...
2
votes
1answer
217 views

Turning off default video output with xrandr when external monitor is connected

I'm new to bash scripting, and I'm trying to configure my video outputs so that my laptop display gets turned off when I connect an external monitor via VGA. That's the script I came up with, pretty ...
3
votes
1answer
137 views

Find and Replace Recursive

I want to modify every file in a directory recursively. I want to replace: <?php with <?php /** * * Copyright (C) MyCompany, Ltd. - All Rights Reserved * Unauthorized copying of ...
7
votes
2answers
667 views

shell script header for best compatibility [duplicate]

Which one is better: #!/usr/bin/env sh #!/bin/sh empty/no header I used to think the 1st one is the best, anyway i've found on some Linux-based systems (like Android) that pathname is missing, so ...
0
votes
2answers
111 views

why is ! character used in shell scripts [duplicate]

I recently encountered a situation where I tried to use ! as a record separator for my string array in shell script. When I used it in my shell script, the script got expanded automatically. An ...
13
votes
7answers
4k views

Test if multiple variables are set

I'd like to make sure that at a certain point of a script, after sourceing a configuration file, several variables are set and, if they are not, to stop execution, telling the user about the missing ...
0
votes
2answers
136 views

how to get the return value of wpa_supplicant?

My question is really simple I want to get the return value of the command wpa_supplicant, when connected to the internet, to know that I am connected or not with a shell script.
4
votes
2answers
653 views

Convert every pdf in the current directory to png

I want to write a bash script to convert every .pdf file in the current directory into a .png file. For example: $ls . a.pdf b.pdf $./pdf2png.sh Converting pdfs to pngs a.pdf -> a.png b.pdf -> ...
5
votes
3answers
1k views

How to read user input in pipe?

Let's assume I have a file named confirmation.sh with the following content: #!/bin/bash echo -n "Are you sure [Y/n]? " read line case "$line" in n|N) echo "smth" ;; y|Y) echo "smth" ...
1
vote
1answer
175 views

For loop not getting executed correctly over ssh

I have a script in which I am reading from a csv file where it contains SourceIp, DestinationIP,Source Ports, Destination Ports. First I am reading the sourceIp and trying to do ssh over it (I am ...
4
votes
3answers
1k views

purpose of run-parts(8) utility

At least under Debian-based systems, there is a run-parts utility in debianutils package which is used in various scripts. For example in /etc/X11/Xsession. It will run all the executable files found ...
3
votes
6answers
5k views

How to reverse a string made of digit in bash?

What is the best way to turn out digits in number? E.g. $ echo 123 | hook 321 $ echo 12358 | hook 85321
2
votes
1answer
237 views

gnome-open execute shell script

Is there a way to execute shell scripts automatically using gnome-open? If I call gnome-open script.sh in the terminal, the script opens in the default text editor. However the shell-script is ...
4
votes
2answers
154 views

Bash script : help file inside the script or in a different file?

I'm writing a script that has the vocation to be a fully featured program at the end. As far as I know, BASH is enough for his purpose (manage PPA's, kinda like Y-PPA). I would like to know how to ...
1
vote
2answers
94 views

Bash script is not working

I wanted to create a script that executes the ls command with the provided arguments. Why isn't it working? I tried running it with for example -R, then it echoes (I echoed the same thing for ...
2
votes
2answers
122 views

I want a script which will take multiple column numbers from a user and reverse the contents

I want a Unix script which will take multiple column numbers from the user and reverse the contents. declare -a param="$@" # enter 0 when exit the insert element echo "Enter the numbers" read n while ...
17
votes
4answers
1k views

How Does Linux deal with shell scripts?

For this question, let's consider a bash shell script, though this question must be applicable to all types of shell script. When someone executes a shell script, does Linux load all the script at ...
2
votes
1answer
1k views

Bash Script getting stuck during execution

I have a bash script that is reading a CSV file , that contains source IP address , destination IP address and destination port. My script is basically doing 2 tests: 1 Performance 2 Connectivity. ...
7
votes
4answers
729 views

Check if 2 directories are hosted on the same partition on Linux

How can I check if /my/dir is on the same partition as /? This is for integration within a script. Bind mounts should be handled correctly. POSIX compatible solutions are welcome.
3
votes
1answer
246 views

Need help decoding bash script

Have following line in bash script, parsing input arguments: ((10#$2 > 0)) 2>/dev/null && shift 2 || shift Basically it helps handling parameters with optional integer subparameter. ...
2
votes
4answers
1k views

Parsing process command-line arguments from pargs in a shell script

I get list of PIDs in my bash scripts (Java processes) and have to analyze their command-line arguments to determine which instance of server each PID corresponds to. At the moment I do it that way ...
0
votes
3answers
1k views

I want to create a zipped output file while keeping the original one

I am new to unix command and I have got one scenario that, I want to create a zipped output file while keeping the original one. I want to do it from Informatica end by using command task or session ...
1
vote
2answers
346 views

Supply input to a program with a password prompt

Is there any Linux command which supplies multiple enter keys to another process which is running in a terminal till the other process dies? For example consider the command yes ' ' | ./ssr-sim ...
2
votes
3answers
5k views

How to delete a line with variable search using sed command

I am new to sed. What is wrong with the sed command on deleting the line which matches the input data? InputData.txt 123, 1234, 1453, Datatodelete.txt 1234,hellofirstline 123,hellosecondline ...
24
votes
7answers
1k views

Should scripts that require sudo fail if they don't have it, or use sudo and prompt?

I have a script which gives me fine-grained control over my backlight brightness and requires sudo to run. It's essentially this: backlight="/sys/class/backlight/acpi_video0/brightness" echo $1 | tee ...
5
votes
6answers
1k views

Will $0 always include the path to the script?

I want to grep the current script so I can print out help and version information from the comments section at the top. I was thinking of something like this: grep '^#h ' -- "$0" | sed -e 's/#h //' ...
0
votes
2answers
95 views

How to search '(+1)' character substring in a string

I want to search for (+1) in a string (which is a GDG dataset name to confirm if it is a GDG) and want to get a binary answer if it has (+1) as part of the string or not. Can some one please help?
5
votes
2answers
9k views

redirecting to /dev/null

I'm reading an example bash shell script: #!/bin/bash # This script makes a backup of my home directory. cd /home # This creates the archive tar cf /var/tmp/home_franky.tar franky > /dev/null ...
1
vote
3answers
318 views

Executing bash shell scripts

I am reading an article on executing bash shell scripts. Method 1: Create a directory for your shell scripts and add the directory to the contents of the PATH variable, so that you can execute the ...
3
votes
1answer
720 views

What's the difference between “==” and “=~”?

Given a string and a hash returned by openssl, why using == doesn't match them correctly but =~ does? Background question: How can I force a script to use more resources?
2
votes
2answers
133 views

Script to Recognize HDDs and run Smartctl

I'm thinking to do a script to recognize which HDDs are in use (sda, sdb, etc) and run a Smartctl on each one that's are in use, but I don't know how can I start, anyone can help me?
-2
votes
2answers
600 views

How to get the port number a program is listening on in a shell script? [closed]

I have a program (beam) running, and I need to figure out which TCP / IPv6 port it is listening on. I know netstat will tell me, but I haven't fully been able to parse its output: ...
3
votes
5answers
358 views

How can I force a script to use more resources?

I'm running a very time-consuming script which takes many hours to end. Watching top I see that it's only taking 5% of the CPU at best, usually around 3%. Is there any way to force the script to use ...
-2
votes
3answers
37k views

How to get IP Address using shell script? [duplicate]

Want to get the IP address using Shell script. Without knowing the eth0 or eth1 or eth2 How to get the particular IP address. I am not interest to get localhost address, want to get private IP ...
-4
votes
4answers
374 views

How to add a 3 lines in a file using shell script? [closed]

I have a file, that file contain 10 lines. And now I want to add 3 lines to end of the file using shell script. After add lines, If I run the script again I don't want to add same lines again. ...
3
votes
4answers
1k views

Bash script to output path to USB flash memory stick

How would I return (output) the path to any USB flash memory stick(s) connected to the local computer using bash (Ubuntu and Linux Mint)? Background: I'm providing users with an automated backup ...
2
votes
5answers
5k views

Command to display Memory usage, Disk Usage and CPU Load

I want to display Memory usage, Disk Usage and CPU Load in the following format: Memory Usage: 33/512MB (6%) Disk usage: 4.2/20GB (23%) CPU Load: 0.01 How do I do that?
3
votes
4answers
227 views

How do I make sure that a script is run exclusively? [duplicate]

So I have a bash scripts that does some things (pull from github, delete folders .. etc ..) pretty basic stuff. I usually run it whenever I need a new version of the web app on the server. The thing ...
1
vote
2answers
716 views

How to write an alias function to make dd show progress bar?

According to this article, by replacing: $ dd if=/dev/sda of=/dev/sdb [additional options] with: $ pv -tpreb /dev/sda | dd of=/dev/sdb [additional options] one can augment the default dd ...
8
votes
7answers
3k views

cron Vs. sleep - which is the better one in terms of efficient cpu/memory utilization?

The Case: I need to run some commands/script at certain intervals of time and for this I have two options - 1. set up a cron-job or, 2. implement a loop with sleep in the script itself. Question: ...
1
vote
0answers
76 views

Better approach to generating and adding contents to files

I have an input file like below. 1 First one 2 First two 3 First three 3 Second three I am generating 2 output files like below. #FILE1 1 First one 2 First two 3 First three #FILE2 1 ...
7
votes
4answers
9k views

Check if $REPLY is in a range of numbers

I'm writing a shell script for Linux, using Bash, to translate any video-file into a MP4. For that, I'm using avconv with libvorbis for audio. Inside my script, I have a question for the user : ...
2
votes
2answers
53 views

How to list all the files which were not created on Thursday

I need to delete old backups but I only want to keep Thursday Backups and delete the rest of the backups. Give me some kungfu tips. I'm on RHEL if that makes a difference.
0
votes
2answers
4k views

Are there any well known and well used shell scripting IDEs for Un*x?

Are there any IDEs targeted at shell scripting, specifically bash and zsh scripts? This means having syntax-highlighting for shell scripts and more importantly debugging environments with features ...
1
vote
1answer
52 views

Creating shell script on Desktop and not getting a prompt?

I have created a shell script on Desktop. Whenever I open it , I get a prompt to either run in terminal, display and etc. How to remove this prompt?
2
votes
1answer
744 views

Find out if files in a folder exist under other name in other folder

Possibly a little incorrect English ahead: There are at least 2 folders. For this, A contains files without extension, usually usernames, and B contains similar files, with '.yml' extension or ...
1
vote
2answers
96 views

What's the difference between print and head?

I know head gives you the beginning section of a file. But in this case, I'm trying to go through my source control and find every file that has a shebang line. And I'm failing to get results when I ...
0
votes
1answer
90 views

Remove directory without `rm -r`

How to remove non-empty directory without using rm -r or find -delete ? I think it is related to unlink, perl or inode