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

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4
votes
2answers
361 views

How can I synchronize processes started in different TMUX panes?

Consider this: tmux split-window -d program1 program2 # this program depends on some side effects produced by program1 In this case, program2 will start before program1 is ready. program1 will send ...
4
votes
2answers
1k views

Get line number in a Bourne shell script

I'd like to be able to print the current line number in a shell script. I know about the $LINENO variable in Bash shells, but it doesn't seem to exist in Bourne shells. Is there any other variable ...
4
votes
1answer
183 views

Discard stdout of a command for t seconds

I am working on some batch scripts involving the following: Run some non-terminating sub-processes (asynchronously) Wait for t seconds Perform other task X for some time Terminate subprocesses ...
4
votes
1answer
771 views

Best way to swap filenames

I need to swap filenames of two files (file and file_1). I'm using the following code for it. mv file .phfile mv file_1 file mv .phfile file This works but is very buggy, It sometimes even results ...
4
votes
1answer
116 views

Script for “battery level reminder”

I want to plug in the laptop battery charger when the battery level goes down to 40% and then plug it out when the battery charge level reaches 80%. And for that reason, I need a script that would ...
4
votes
2answers
90 views

Using $ in a password

Lets assume that password of my server is Abcd$1234 I am trying to ftp a file from other server to my server using the following in shell script ftp -inv (IP) << EOF user Username Abcd$1234 ...
4
votes
1answer
213 views

returncode of command in a pipline [duplicate]

The following script runs on Solaris using /bin/ksh and on Linux using /bin/sh cmd | tee -a cmd.log | tail exit $? The output of cmd is saved in a file cmd.log and the last lines are displayed on ...
4
votes
1answer
396 views

output while reading keyboard input

I'm trying to write a script that will ssh into a box, start a processes that needs to be monitored (by a human) for success or failure then move onto the next box and repeat. I've been trying to use ...
4
votes
2answers
857 views

Simple Shell script to log disk space

I'm working on automating collecting disk space on a group of servers. In a standard terminal, if I run: ssh server1 ssh server2 df -h Then I get the output of the command, just fine. ...
4
votes
1answer
1k views

Validate AIX Password for root from script

Looking for a way in a shell script to validate the password for for root on an (AIX) matches a standardized plain text password. This query is similar to another one on this site. I have access to ...
4
votes
2answers
335 views

Script for emulating Windows [Win]+[Arrow] keyboard shortcut

I am running Fedora 14. I would like to (at least partially) emulate the behaviour of Windows when you hit Win+Arrow Key. That is, I would like it to "snap" to the left/right sides of the screen. I ...
4
votes
1answer
37 views

Simple problem, Long read: How to overwrite file residing on ESP at Linux boot

First, foundation. Here is my setup: I have a 64-bit dual-boot system running Windows 7 and Linux Mint 17 Cinnamon. I use rEFInd to graphically choose which system to boot. A little bit about ...
4
votes
0answers
213 views

How to write a shell script to run multiple command in different screen sessions?

My goal is to write a zsh script in order to create multiple screen sessions and run separate commands on each of them. I would also like to check at the beginning of my script if there are any ...
4
votes
2answers
510 views

How do I run a script when I switch between keyboard layouts

I use more than one keyboard layout, and I would like to find a way to run a script when I switch between them. Is this possible? So far, I can assign a shortcut for a script like this: #!/bin/bash ...
4
votes
1answer
738 views

Scoping variables in ksh

In ksh, I have two variables with the same name , one global , other one is local to a function #!/bin/ksh LOG_FILE=lf function exec_script { local LOG_FILE=f print $LOG_FILE } exec_script ...
4
votes
2answers
20k views

How can I run a shell script as a daemon under Redhat?

I've got a shell script, which is essentially a one liner with some logging, which I'm trying to run this from an init script. I'm using the daemon function inside of /etc/init.d/functions to run it, ...
4
votes
0answers
105 views

How to code shell script with command line arguments like -la [duplicate]

Possible Duplicate: How do I handle switches in a shell script? I know how to deal with simple arguments $1-$9 but I don't know how to code it with such as -la, for example ls -la. Could ...
3
votes
5answers
902 views

Lots of elif, is there a better way?

I have a Bash script that looks like #!/bin/bash # FECHA=`date +%j` if [ $FECHA -eq 40 ] then echo "Esta semana le toca preparar el café a Osvaldo" | mail -s 'Café' mailgroup@somedomain.mx ...
3
votes
7answers
3k views

Problem in splitting a string using awk or cut command

I have a properties file which has a password field (key value pair) PASSWORD=NDhhHcsOBofXUdUzGw5B0Q== I am trying to get the value in my shell script using the awk command password=`awk -F "=" ...
3
votes
2answers
502 views

How to ls without recursive

I am trying to ls some files with a pattern in a directory. I only want to scan the first level not recursive. My script: for i in $(ls $INCOMINGDIR/*$BUSSINESSDATE*) do echo $i; done Above ...
3
votes
2answers
4k views

Scripting `rm` and `rm -i`

I want to create a script that whenever there are more than three files being removed, it invokes rm -i by default. I know it will go in initialization files but can't seem to get it working. So far: ...
3
votes
2answers
485 views

How does a script/program executes in unix?

I have a doubt about the execution pattern of a unix script. For example a script containing lines: command B function C() { Myscript // Myscript is a script command D } command E and ...
3
votes
5answers
318 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 ...
3
votes
5answers
852 views

What are the special characters to print from a script to move the cursor?

I found that by printing \r from a script the cursor moves to the beginning of the line. What character will move the cursor up one line? Where is a list of these special characters? EDIT: Working ...
3
votes
4answers
4k views

List of servers to check for SSH availability

I have a list of IP address that I need to SSH to and log if I could get to them. I would use a Ping script, but DNS might have already reassigned the address. I do not care about the ones I can't get ...
3
votes
1answer
522 views

Why is 'kill -9' killing browser as well as server?

I sometimes have to use kill -9 as a last resort to kill my rails server. Unfortunately, I have to do that often enough that I wrote a helper function in my bash_profile to do it. If I do it manually ...
3
votes
7answers
380 views

get parts of string using shell script

I have one string as /ip/192.168.0.1/port/8080/ I want to get two separate variables which will contain port and IP like. 192.168.0.1 and 8080 as I know /ip/ and /port/ will be there always I ...
3
votes
6answers
4k 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
3
votes
2answers
2k views

When sh is a symlink to bash or dash, bash limits itself to POSIX-compliance, so it should be 100% compatible with sh?

From Difference between bash and sh: ABck to the question: If you have /bin/sh as a link to bash, then bash will not behave the same when called as /bin/sh as it does when called as /bin/bash. ...
3
votes
3answers
596 views

Replace %20 with a space in filenames? [duplicate]

I have a list of files that are using %20 to indicate a space in their names. I'm currently trying to do the following to change them all from %20 to a space " ". for x in *.txt do mv $x $(echo $x ...
3
votes
2answers
2k views

exec < filename - what does this do?

I have found the following code snippet (sh): TESTFILE=$TEST_PATH/test.out if [ -f $TESTFILE ] then exec < $TESTFILE else echo "$TEST_PATH: no test.out file" fi ...
3
votes
5answers
4k views

Script to list only files of type ASCII text in the current directory?

How to write a shell script which searches the current UNIX directory and returns the names of all files of type ASCII text?
3
votes
2answers
2k views

How to write a script to execute files in multiple directories

How do I write a script to execute the files in multiple directories? The problem is this: I have many directories, and each has a data file to be read and analyzed by a python script (say, a.py). I ...
3
votes
4answers
277 views

Bash (Ubuntu) - Strings in while loops?

I am trying to create a while loop in bash that won't continue until the user enters the word "next". I can't seem to figure out how to use strings for the condition though. #Beginning of code ...
3
votes
4answers
220 views

Does cron jobs per se represent a significant burden on a modern system?

I'd like to run a pretty simple script (is there a dir with name x in dir y if so move it to dir z–and x will only be there about once a day) every 15 seconds or so (one minute divided into 4*15 ...
3
votes
3answers
224 views

Zsh function with su and echo

I'm trying to add a function to my .zshrc that makes adding new USE flags to my /etc/portage/package.use file easier. Normally, I'd have to do su -c 'echo "net-misc/aria2 bash-completion bittorrent" ...
3
votes
2answers
2k views

Passing a bash command-line argument containing a dot

How can a command-line argument containing a dot (.) be passed? Are there any escape sequences for capturing characters like dot? The following invocation of a bash-script from the shell does not ...
3
votes
3answers
4k views

Error handling in shell script

I wrote a shell script run_script.sh, which includes a step which creates an empty file run_script.lck. Everytime the shell script was called by the cronjob, it will check for the existence of ...
3
votes
2answers
10k views

How to get the char at a given position of a string in shell script?

How to get the char at a given position of a string in shell script?
3
votes
2answers
123 views

Extract text including parens

I have some text like this: Sentence #1 (n tokens): Blah Blah Blah [... ... ...] ( #start first set here ... (other possible parens and text here) ) #end first set here (...) (...) Sentence #2 ...
3
votes
4answers
235 views

Test if command accepts a specific option

What is the preferred way to test if a command takes an option? What are the caveats? As a motivating example, at login my shell aliases grep to add several --exclude-dir options but this option is ...
3
votes
3answers
294 views

Preventing a specific space from being expanded in a variable

In bash how do you avoid a specific space from being expanded in a variable? Lets say I have this JAVA_OPTS="-Xmx1g" JAVA_OPTS="$JAVA_OPTS -XX:OnError='/path/to/a/script.sh %p'" function args() { ...
3
votes
3answers
449 views

Pipe in a shell script

I have done this little script : #! /bin/sh path="foo" while touch $path ; do path=./${path} done echo "echec avec le nom $path qui fait" echo $path|wc -c echo "caracteres" How can I ...
3
votes
1answer
181 views

CPU is free, yet bash script not utilizing all CPU resources

I ran a simple script to generate a large (10000000 lines) csv file with 6 fields in which some fields changed in each line/row, using a while loop. The machine had all (32) CPUs free, lot of RAM (~31 ...
3
votes
4answers
1k views

Replacing pattern after nth match is found on each line?

I have a file containing lines: india;austria;japan;chile china;US;nigeria;mexico;russia I want to replace all the occurences of semicolon on each line with e.g. ;NEW;, but starting from the 2nd ...
3
votes
5answers
1k views

Remove lines based on pattern by keeping first n lines

I need to remove lines from a text file based on pattern but I need to keep the first n lines of that pattern. Input % 1 % 2 % 3 % 4 % 5 text1 text2 text3 output %1 %2 text1 text2 text3 I used ...
3
votes
5answers
262 views

Awk - output the second line of a number of .dat files to one file

I have searched through previously asked questions and can't find an answer to what I am trying to do. note, I am new to linux. I have multiple files something like: (in reality i have 80) file1.dat ...
3
votes
3answers
544 views

Determine maximum column length for every column in a simplified csv-file (one line per row)

To determine the maximum length of each column in a comma-separated csv-file I hacked together a bash-script. When I ran it on a linux system it produced the correct output, but I need it to run on OS ...
3
votes
3answers
1k views

How to move the first x files

I have this huge folder with thousands of unordered files. Is it feasible to move the first 5000s to a subfolder via the mv command? For now I move files with mv *some_pattern* ./subfolder1/ ...
3
votes
3answers
617 views

Determine the last 7 days backup size

Consider I have a folder /home/abdul/backup which contains .gz file for the past 1 year...My requirement is to get the size of last 7 days...