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

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2
votes
1answer
227 views

indirect variable expansion in POSIX as done in bash? [closed]

Is it possible, or is there some elegant hack to do indirect variable expansion in POSIX as can be done in Bash? For context, I'm trying to do the following: for key in ${!map_*} do # do ...
12
votes
7answers
5k 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 ...
3
votes
1answer
118 views

Count and merge consecutive patterns

I'm searching for a short snippet to find, count and merge consecutive duplicates using standard tools or a common scripting language. Say our input is: 1 2 2 2 7 22 a b b c c c c c d dd 2 2 c c ...
6
votes
2answers
6k views

Associative Arrays in Shell Scripts

I saw a trick for implementing associative arrays in a shell script. For example print array["apples"] could be scripted as echo \$array$key where key=apples. However, there was no mention of how to ...
2
votes
2answers
631 views

How do I check that a filename conforms to a pattern?

I'm tasked with writing a shell script which checks that a filename conforms to a specific pattern and I'm not sure how to go about it. The filename should follow a pattern which looks like: ...
7
votes
2answers
2k views

Local variables in zsh: what is the equivalent of bash's “export -n” in zsh

I'm trying to contain the scope of a variable to a shell, and not have children see it, in zsh. For example, I type this in .zshrc: GREP_OPTIONS=--color=always But if I run a shell script with the ...
0
votes
2answers
973 views

bc removes decimal point

This is related to Shell script too slow for output to Conky This code is nearly perfect: stdbuf -oL jack_cpu_load \ | grep --line-buffered "jack DSP load" \ | stdbuf -oL cut -d' ' -f4 \ ...
0
votes
2answers
1k views

Using AWK to delete line and output result

I have a text file and manage to find the line through output comparison. With the book title and author name. awk -F ':' '/KungFu Feet|Chuck Norris/' test.txt Kungfu Feet:Chuck Norris:12:1:1 Is ...
2
votes
3answers
4k views

Backup files with tar command and progress bar? [duplicate]

Can I see a progress bar or something not only ust the terminal screen output while backing up? Here is my shell script that I used backup with tar command: # !/bin/bash DATEJOUR=$(date ...
3
votes
3answers
391 views

Shell script too slow for output to Conky

I want the output of stdbuf -i0 -o0 -e0 jack_cpu_load | sed -n 's/[A-Za-z]*//g;s/ //g;s/.\{4\}$//;9,$p' to be displayed in Conky but, I suspect, Conky is starting the script with every refresh and ...
1
vote
1answer
431 views

how to send keyboard signal using a shell script

I have an application in graphical interface that when I run it, it's not opened in full screen mode, but when I use the keyboard shortcut Alt+Ctrl+M , it becomes fullscreen, I want to change the ...
2
votes
1answer
65 views

Pipe output of jack_cpu_load through sed

In the shell, when I pipe jack_cpu_load through sed, or cut, no matter what options I use it stops printing just before the lines I want to see. jack_cpu_load | sed -n 8p will print: Jack: ...
1
vote
1answer
159 views

Unknown syntax in /etc/rc.d/init.d/functions

Looking at the file /etc/rc.d/init.d/functions, I can see the following is declaring a number of variables as local variables. However, why are the variables killlevel and pid_file have an equal sign ...
4
votes
2answers
1k 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
5answers
343 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 ...
-2
votes
1answer
426 views

automatic capturing top output by cronjob CENTOS 6.5 x86_64

I have this command: top -n 14400 -a -b -d 1 > /toplogfile.txt I want to make a script which is run by cron every day to capture top output, and if it is possible gzip the output file after the ...
1
vote
1answer
447 views

How would I detect a non-login shell? (In Zsh)

I want to create a script that runs when a Zsh instance starts, but only if the instance is: Non-login. Interactive I think I'm right to say .zshrc runs for all interactive shell instances, ...
1
vote
3answers
1k views

How to get numbers by using regular expression, but only last one

In this example I can get 00. expr match "00 foo 99.jpg" '[^0-9]*\([0-9]\+\).*$' I want to know how to get last number from string, in this case 99 by using regular expression. The string may ...
2
votes
1answer
2k views

Changing text color in c-shell

I can change the text color in the terminal permanently by adding this: export PS1="\e[0;31m[\u@\h \W]\$ \e[m" to the .bashrc file. Now I have to go into cshell, what is the corresponding way?
0
votes
0answers
102 views

Is there a difference between `command rspec` and `rspec`?

I want to call bundle exec rspec if Gemfile exists in current directory, and if it doesn't exists, call rspec itself. So I wrote like this. function rspec() { if [ -e 'Gemfile' ]; then echo ...
5
votes
5answers
335 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 ...
0
votes
3answers
154 views

How can I add a script to embedded Linux

I have a script (let's say Hello World), that I want to include to my embedded Linux. I'm using Buildroot and want to start the script in Busybox. But because I'm cross-compiling for the target I'm ...
1
vote
1answer
42 views

Where can I find documentation on shell script syntax for using a regex within a variable construct?

I'm debugging a shell script (which I didn't write) that contains this loop: read line < "$pid_file" for p in $line ; do [ -z "${p//[0-9]/}" -a -d "/proc/$p" ] && pid="$pid $p" done ...
0
votes
1answer
949 views

shell script - echo command not printing in proper sequence

I have the following testfile.txt: string1 1 string2 2 string3 3 string1 2 string2 4 string3 6 string1 3 string2 6 string3 9 I have the following script: #!bin/sh ...
0
votes
0answers
38 views

Bash script to identify which init system the system currently using [duplicate]

I have to create a script that will mount my /usr folder as aufs. I compressed it using squashfs. I've managed to install a working systemd init in ubuntu which I am currently using. Because the ...
0
votes
1answer
144 views

Debian one time setup after reboot

I have a pre-configured server based on Debian with some services. I, now, need to deploy it in different networks. Is there any solution to run a one time script after reboot which asks some ...
0
votes
1answer
200 views

shell script - reading from standard input versus a file

I have the following input file in.txt: a b c a b c I have the following script test.sh: # display unique rows while read line do echo $line done < $(cat "$@" | sort | uniq) # display all ...
2
votes
0answers
543 views

Number comparisons in BusyBox ash

I have the following script that extracts data from the EXIF command on my BusyBox ash-based system. I parse the date tag from the end of the file and use case as a final check to ensure the format ...
1
vote
2answers
722 views

Cygwin - Shell Scripting (eval and echo)

I have the following file f1.txt: A=0 A=\`expr $A + 1\` and the following script file s1.sh for line in $(cat testfile.txt) do echo "$line" # eval $line done echo $A When I run the ...
3
votes
2answers
1k views

Bash Script To Find Debian Release Number from /etc/debian_version

The following is what I'm currently using for testing the version of Debian. Instead of doing it this way, can I make it more succinct? #!/bin/bash VERSION=NONE if [ $(cat /etc/debian_version) == ...
3
votes
1answer
145 views

Can someone clarify this Bash script

I'm learning something about Bash scripting, and I came across this example: The task is to write a Bash script that reads a file, given with the first argument, pulls out those records that have the ...
1
vote
1answer
338 views

removing data from txt file

I have a comma-delimited giant file that was exported from a database. The file has this format Date,n1,n2,n3,n4,n5,n6,color,type,reference 10-Jan-2000,344,13,21,2,55,3,"rose garden" ,3444,32 ...
2
votes
3answers
852 views

To assign variable from a file separated by delimiter

I have a text file with datas as below separated by delimiter: 1000:Tom:user1 1002:Jerry:user2 1003:Victor:user3 1004:Jason:user4 I need to run a while loop (any loop) to fetch details from first ...
3
votes
3answers
858 views

Bash script to delete a file called index.html recursively

I need a bash script (not sure how to write the actual .sh file) which I could set to be run by cron every minute and that would delete files with the name index.html that are in a specific directory ...
4
votes
3answers
1k views

Help Shell script to pass variables to rsync

I'm trying to create a simple wrapper shell script for rsync. When I send file names to my script, rsync can never seem to identify the correct location. The file names have spaces in them. I've tried ...
0
votes
2answers
11k views

Shell scripting: -z and -n options with if

I have a shell script where we have following lines if [ -z "$xyz" ] and if [ -n "$abc" ], but I am not sure what their purpose is. Can anyone please explain?
2
votes
1answer
2k views

“stdin: is not a tty” mails for running scripts as cron jobs

I have several shell scripts (bash) which are started by cron. Every time a script is executed I get an email saying "stdin: is not a tty". Can someone please tell me how to fix this? All scripts run ...
5
votes
2answers
2k views

How to append multiple lines to a file without last newline?

I have a very long string that is split in chunks. I want to append them to a file without putting the newline character using bash. Example: First append cat >> abc.sh << EOL echo "bla ...
0
votes
1answer
55 views

Prepare a computer for being firstly used in my home network with a BASH script is possible?

I need a script that detects the computer joined the same home network and standardize its folder structure. For example If there's A, B and C computers in a network which are configured to have a ...
4
votes
1answer
85 views

What's the difference between sh script and sh < script

What's the difference between sh myscript and sh < myscript I played around and they seem to have the same effect. Are they equivalent?
6
votes
2answers
468 views

Expansion of a shell variable and effect of glob and split on it

This post actually contains two separate questions but I think grouping them together will give some more context. I have gone through this question on quotes around variables but I do not quite ...
2
votes
1answer
261 views

Bash:source files without fullpath?

if I source the script file without pre-path definition, it does not work. What is happening below? I have got a go1 function in the file simply printing $PWD. $ bash --version GNU bash, version ...
1
vote
1answer
37 views

Problematic quotations

#!/bin/ksh typeset FILE_SIZE1=$(stat -f '%z' test.txt); typeset -r BK_STATARGS="-f '%z'" typeset FILE_SIZE2=$(stat ${BK_STATARGS} test.txt); echo without arg var ${FILE_SIZE1} echo with arg var... ...
1
vote
2answers
517 views

Script to su -c into a screen is not working as intended

I'm working on a script that will allow me to load up a screen from a user via sudo and su -c. However, when I use it, it will just show the shell of the user: sudo su -c "script /dev/null; screen -r ...
2
votes
2answers
184 views

Help with 64-bit integers in scripts?

Maybe I'm overthinking this (although I don't think I am)....or maybe there's a neater way of solving my problem ? I have a requirement that if a file is larger than 1GB, it gets split into smaller ...
0
votes
0answers
20 views

Multiply 2 array index variables shell programming [duplicate]

How do i multiply 2 array index variables given the following foo=(1 2) bar=(0.1 0.2) foobar=$((foo[1]*price[1])) # this is wrong echo "$foobar" Current output : 0 Correct/Expected output : 0.4
2
votes
1answer
190 views

How to FILTER the files with filename and then DELETE the OLDEST file from there? [duplicate]

I create and keep the following automated backup files e.g.: fruits_29-12-2013.gz fruits_30-12-2013.gz fruits_31-12-2013.gz sweets_01-12-2013.gz sweets_02-12-2013.gz sweets_03-12-2013.gz .. ...
3
votes
1answer
423 views

Compare users out of an array with /etc/shadow file

I want to check for all users who do not have a password set. For example, a user with the following entry in /etc/passwd test01::15164: ...* has no password set. I would like to list all such ...
2
votes
2answers
200 views

Show a sliding window of output from a program

I want to run a command (rsync -av) and only display 10 lines of output at any time. I have found a similar post, but I don't want to redirect it to a file. I want the output to be displayed ...
3
votes
3answers
239 views

USB device to be detected at the “same” /dev point always?

In Linux (actually I'm with CentOS v6.5), whenever I plug in my USB Terminal/Character Device (some kind of USB Adapter) for the first time (after booted), it is detected at: /dev/ttyUSB0 But ...