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

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How to write repeated free-form strings to a file, as fast as 'dd'?

dd can write repeating \0 bytes to a file very fast, but it can't write repeating arbitary strings. Is there a bash-shell method to write repeating arbitary strings equally as fast as 'dd' (including ...
4
votes
4answers
996 views

How to get the network status (online/offline) and attribute it to a variable in shell script?

How to get the network status (online/offline) and attribute it to a variable in shell script?
4
votes
3answers
134 views

Log monitoring using shell script

I would like to monitor a log file for errors and then send an email to administrators. The log file contains data like below 11 Aug 02:30 Service1 restarted 11 Aug 05:35 Service1 restarted 11 Aug ...
4
votes
3answers
147 views

Get date of next Saturday from a given date

I want the date of the coming Saturday after a given date. For example, for $date1="30-AUG-2015", I want the result 05-SEP-2015. I have tried all the commands below with no success: samba@samba:~$ ...
4
votes
3answers
440 views

Tool to generate TCP traffic

I want to generate a TCP traffic starting from the port 0 to the port 65535. 1 tcp packet for each port with 1ms between 2 packets. The generator should not care if there is a TCP ACK or not. Are ...
4
votes
4answers
184 views

list folders and their content

I'd need a file reporting for each folder the content and the name of the folder itself. If I do ls -l * I have (this is just a subset of hundreds of folders) ...
4
votes
1answer
1k views

bash permission denied but sh works

A little script of mine on a mounted windows partition refuses to be executed directly (shebang is #!/bin/bash), but interestingly calling it with bash/sh works. The script is simply a collection of ...
4
votes
1answer
172 views

string in a file as a variable

I have a conf file content like below. file.conf: key="name" value="pswd" Now I want write a script to having two variable like above script.sh key="name" #key as variable value="pswd" ...
4
votes
4answers
419 views

Text files containing their own name

I need to find in certain directory and all its' subdirectories all text files that contain their own name. How do I do this? (preferably without awk command)
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4answers
1k views

extract every nth character from a string

I am trying to figure out a solution for this question. My approach to this problem so far is as below. Append all the characters together to make it a long string. After the above step, remove ...
4
votes
5answers
10k 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?
4
votes
2answers
5k 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, ...
4
votes
4answers
666 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. ...
4
votes
5answers
1k views

Is there a way to listen to process?

I want to know if there is a way to listen to a process in linux & unix - when it ends and what's the exit code of the process(script). I dont want to write a script that will run X seconds and ...
4
votes
1answer
2k views

Use the terminal's autocomplete path feature for input to a shell script

I want to make a script that: (1) Gets a path giving the user the ability to use tab to autocomplete, then (2) gets a filename from the user, and then (3) creates a file at that path with extension ...
4
votes
2answers
7k views

How do I capture the return status and use tee at the same time in korn shell? [duplicate]

Consider Source code: 1. Parent.sh #!/usr/bin/ksh # No tee ksh Child.sh; exit_status=$?; echo "Exit status: ${exit_status}" # Using tee ksh Child.sh | tee -a log.txt; exit_status=$?; echo "Exit ...
4
votes
2answers
3k views

How to run "find -exec <script> {}\;

I have a script that changes the properties of the files for a folder. Here is the example tree: dir 1 --file 1 --file 2 --file 3 dir 2 --file 1 --file 2 dir 3 --file 1 ...
4
votes
1answer
3k views

How to find out common elements between two files?

For an example, I have 2 files having following info: File #1: 12 13 14 15 File #2: 12 1 13 2 14 2 15 6 16 7 17 8 Output File: 1 2 2 6 In the output file, I want only the second column ...
4
votes
2answers
2k views

How to configure mailx to support Gmail?

How can I set up mailx to send messages to my Gmail account? What I do now is run the command: mail -s "hello kid" mymail@gmail.com It freezes and does nothing. I tried some variations, but all of ...
4
votes
2answers
2k views

zsh: excluding files from a pattern

Say I have the following files: |-- bar `-- foo |-- type_A_1 |-- type_A_2 |-- type_B_1 |-- type_B_2 |-- type_B_xx |-- type_B_xx `-- something_else I thought the ...
4
votes
3answers
377 views

Delete files in a directory which are also in another directory

I copied a directory using this: cp -r dir/ ../../ without thinking and realized that it copied the contents of dir instead of actually dir to the above directory. Now I have a mess of files I need ...
4
votes
3answers
8k views

Simple Shell Script with Arithmetic issue… ** is giving me trouble

When I run this script I get this error: ./myscript.sh: 16: arithmetic expression: expecting primary: "1 ** 1" When I run this shell script with bash, as in #! /bin/bash on the first line, the ...
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votes
3answers
1k views

renaming files without the **rename** command

I have a directory of files, Measurements Panama 2009-03-22 Session1.xml Measurements Panama 2009-03-22 Session2.xml Measurements Panama 2009-03-22 Session3.xml Measurements Panama 2009-03-22 ...
4
votes
3answers
170 views

Bash script: do something one time inside a loop then stop, but continue looping

I have a Bash script that checks my laptop battery and sends me an Android notification (via shuttle, a Bash script I wrote that serves as a cli interface for the Pushbullet API). It works nicely, but ...
4
votes
4answers
311 views

Merge two files

I have this file1.txt deiauk 9 kespaul 8 luktol 7 titkur 6 and other file2.txt kespaul b deiauk a And I want to merge both files in one by first value, so my result should be deiauk 9 a ...
4
votes
3answers
443 views

How to use printf and %s when there are color codes?

I had these lines: if [[ $# -eq 0 ]]; then printf "$fail_color Error - Function: $function, Line: $line_number \n" printf "do_test: Third parameter missing - expected result\n" exit 1 fi This ...
4
votes
3answers
355 views

How to append a date to all files in a directory without touching sub-directories via bash script

I'm currently taking a class for Operating Systems and we're learning to do bash scripts as part of the curriculum. I need to append the date to all the files in a directory without touching ...
4
votes
2answers
447 views

Script working on Mac but not Ubuntu

The script executes on a Mac machine and creates the output file, although on an Ubuntu machine it generates error message. Bash shell is used on both instances.: 1 - /var 2 - /etc : 1 : bad ...
4
votes
3answers
417 views

Better way to run single for loop instead of two for loops

This works but the way I did this is kind of silly. Is there a better way to do this? for e in $(ipcs | awk '{print $2}'); do [[ "$e" = "Semaphore" ]] && break echo $e ipcrm shm ...
4
votes
2answers
115 views

Problem with read variable from AWK

I'm trying to get memory info by this command: #!/bin/bash set -x cat /proc/meminfo | grep "MemFree" | tail -n 1 | awk '{ print $2 $4 }' | read numA numB echo $numA I'm getting this + awk '{ print ...
4
votes
2answers
224 views

Spliting `File` and `directory name with space' via shell script

I've got a file called Files.txt having following content: TestApp/Resources/Supporting Files/main.m TestApp/Resources/Supporting Files/AppDelegate.h TestApp/Resources/Supporting Files/AppDelegate.m ...
4
votes
3answers
7k views

Range of the command cut in unix

I'm trying to make a shell script, I want to cut a string using the 'cut' unix command, as follows: namecmpaux=$(echo $namecmp |cut -c0-19) But when I run the shell tells me the following error: ...
4
votes
5answers
407 views

Join two files, matching on a column, with repetitions

How can I get two files A and B, and out put a result like this: File A: 001 Apple, CA 020 Banana, CN 023 Apple, LA 045 Orange, TT 101 Orange, OS 200 Kiwi, AA File B: 01-Dec-2013 01.664 001 ...
4
votes
3answers
1k views

Reading a binary file as an array of bytes or 16 or 32 bits using shell script

I am working on ARM-based modem Linux host machine and I need to read a bin file as an 8-,16- or 32- bits array. I basically need to encrypt the file in question and was thinking of just XOR-ing the ...
4
votes
2answers
10k views

list all files newer than given timestamp and sort them

I want to list all files (sorted by date) that are newer than timestamp in format 20130207003851 in directory /tmp only. Subdirectories can be omitted. Using SUSE Linux Enterprise Server 11. The ...
4
votes
4answers
3k views

Make cp return an error value if the target exists

Is there a way to make cp (from GNU coreutils on Linux) return a nonzero value in case the target file does already exist? Or is there any other small utility which is commonly available and which ...
4
votes
2answers
12k views

Bash shell script to locate and remove substring within a filename

I am trying to write a bash shell script in Mac OS X 10.6 (which is called by an Automator Action) to rename TV show DVD rips that I have named badly over the years. I want to remove part of the text ...
4
votes
2answers
120 views

Run an app with a window manager behind in a separate X server

I want to launch an app in a separate X server. It needs a window manager behind it, though. I created a script #!/bin/sh x-window-manager & my-gui-app and launched it with xinit ...
4
votes
1answer
71 views

How do I find a file name that's exactly 8 levels deep?

I'm using the 'find' command to search for files in a backup system. I want to find all file names containing a certain string (e.g. 'XYZ') that are exactly 8 levels deep. Is there a find syntax that ...
4
votes
4answers
398 views

How to Check the existence of multiple files in a directory and zip the same

I am facing an issue while checking the existence of files ending with the same string/pattern. The file names might be as follows abs_123.unl xyz_123.unl Currently my code is as below and working ...
4
votes
5answers
535 views

How to delete files from a folder which have more than 60 files in unix?

I want to put a script in cronjob which will run in a particular time and if the file count is more than 60, it will delete oldest files from that folder. Last In First Out. I have tried, ...
4
votes
1answer
102 views

Why does 'jobs' always return a line for finished processes when run in a subshell within a script?

Normally, when a job is launched in the background, jobs will report that it is finished the first time it is run after the job's completion, and nothing for subsequent executions: $ ping -c 4 ...
4
votes
1answer
160 views

Can I refer to a global variable even if a locally scoped one exists with the same name?

If I have a variable x total=3 and then a function function A () { local -i total=0 } Is there any way I can update the 'global' total variable total from within function A ?
4
votes
1answer
145 views

cmd2 `cmd1` vs cmd1 | xargs cmd2

I'm trying to find a file with find and then pass the found path to sqlite3. I'm only dropped into the sqlite> prompt if my command is of the form: sqlite3 `find . -type f -iname "*.db" | head ...
4
votes
2answers
119 views

Is there a way to have a function in my bash script auto run on any command error?

I'm writing a shell script that needs to do a bunch of commands and every command depends on every previous command. If any command fails the entire script should fail and I call an exit function. I ...
4
votes
3answers
245 views

How to convert an unsigned decimal (less than 1<<32) to 4 bytes (binary) in bash?

Example: $ decimal=$(( RANDOM << 17 | RANDOM << 2 | RANDOM >> 13 )) $ echo $decimal $ printf "%08x" $decimal | xxd -r -p >bytes The result is in bytes file. Can it be done in ...
4
votes
3answers
10k views

Script to ssh and run a command doesn't work

Below is the script. I wanted to login several servers and check for the kernel version. #!/bin/bash #input server names line by line in server.txt cat server.txt | while read line do sshpass -p ...
4
votes
2answers
4k views

Copy ssh public key to multiple Linux hosts

I am trying to copy .ssh/id_rsa.pub from our central server to multiple servers. I have the following script which I usually use to push changes to the different servers. #!/bin/bash for ip in ...
4
votes
1answer
4k views

Bash Script Permission denied & Bad Interpreter

I'm on a kali linux 64 bit. I have created a python script which takes 2 arguments to start. I don't want to type out every time the exact same paths or search in the history of the commands I used ...
4
votes
2answers
627 views

Shell script (bash) to add or replace the license text contained within .c , .h and makefiles?

I have a set of *.c , *.h and Makefiles in a folder where some files contain the license text and some files don't have any license text. So I need a shell script where I can add license text if the ...