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

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1
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2answers
37 views

Re-print an array in a certain format?

I wish to take 10 random lines of file, which is 100 lines long. First, I randomly generate 10 integers between 1 and 100 (inclusive) with ind=$(shuf -i 1-100 -n 10 | sort -n) Then, I wish to use ...
2
votes
3answers
59 views

How can I count the number of times a phrase appears in a file, and format it neatly?

I have a log file I am trying to pull data from. It is formatted like so, and lists when certain modules are checked in and out: 19:50:26 (license_manager) OUT: "certain_module" doej@server.domain ...
1
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3answers
48 views

Find the complement set of an array?

Following from this question, where I wish to extract 10 random lines from a file, I now wish to also have the remaining 90 lines as a separate file. Since the document has 100 lines, indexing from 1 ...
2
votes
3answers
48 views

Specific column level substitution

If I have a file with columnar entries, is it possible to substitute specific entries from a specific columns only and save changes to the same file?? Example a file abc.txt: SR|FRUITS|COLOR| ...
1
vote
2answers
39 views

In ShellScript, how to call a function after completion of function which is already running?

My script involves three shell functions. Two running in parallel. I have to call a third function when the two parallel running function completes it's execution. How to call that third function? ...
1
vote
5answers
37 views

Output to variable with an indirect command (eval)

What is wrong with this indirect command when run with eval ? #!/bin/bash OS=AIX host=myhost CMD_AIX="(o=\`host \"$host\" \`)" CMD=\$CMD_$OS echo $CMD eval echo $CMD eval "$CMD" Ouput: $ ...
12
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5answers
9k views

how do I trim each line in bash?

I would like to remove all leading and trailing spaces and tabs from each line in an output. Is there a simple tool like trim I could pipe my output into?
1
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2answers
4k views

Type URL and show HTTP status

I want to make a shell script where I type an url and it returns me the status code.So far I've tested wget is there any other cause it has the tendency to save whatever you run. Then I tried to some ...
1
vote
1answer
21 views

Why does bash try to execute strings in a string substitution?

My script is supposed to take input from a pipe and replace newline characters with commas, using the bash's string substitution: #! /bin/bash read -d -r input echo $input $input=${input//\n/,} ...
1
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2answers
39 views

Substrings in shell script

Am trying to get a substring from a string but am getting the error: ${curr_rec:3:4}: bad substitution #!/bin/ksh get_file_totals() { if [ -e "$file_name" ] then IFS='' ...
20
votes
2answers
26k views

Empty the contents of a file

I am aware of three methods to delete all entries from a file. They are >filename touch filename filename < /dev/null Of these three I abuse >filename the most as that requires the ...
4
votes
6answers
132 views

Append something to each list in a file

I have a file, lists.txt, that looks like this: // stuff at beginning of file var list1 = new Array(); i = 0; list1[i++] = 'a'; list1[i++] = 'b'; ... list1[i++] = 'z'; var list2 = new Array(); i = ...
2
votes
0answers
35 views

BASH: Fifo troubles - seems selective about input

So I am having a problem with a BASH service in Debian 7 that I've been working on for quite a while and that randomly started having trouble with its fifo, or so it seems. It is based on kind of your ...
2
votes
1answer
53 views

Checking if a specific key is pressed in shell script

Is there a way I can check if a specific key is pressed in a shell script which is running in background. Consider I am running a shell script which has to play a play list of songs as soon as I press ...
1
vote
1answer
44 views

POSIX shell scripting and performance tuning [on hold]

Nowadays, I'm researching for performance tuning for shell scripting , And I have been prevented to POSIX shell scripting, However it's only a standard, But I think it's rathar than standard for do ...
2
votes
4answers
98 views

Script to log temperature

I have been trying to write a BASH script to log my raspberry pi's temperature. My plan is to run it as a crontab every 15 mins or something. However I keep getting errors, I think it's something to ...
4
votes
1answer
39 views

Settings environment variables from a file

I want to have a file (outside of git) that contains certain environment variables. While a script (which is in git) needs to read them and export to env. My current implementation works for ...
2
votes
3answers
125 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
2answers
23k views

Assigning the output of a SQL query to variable

I am connecting to oracle database and firing a query and assigning the output to variable But when I echo the value of the variable it doesn't get printed correctly. count=`sqlplus -s ...
1
vote
3answers
45 views

Find a file with the extension .csv in a directory matching a pattern

I have a folder in which I have many subfolders. The Root folder name is allCSV and sub foldername is will be like a_date(s), b_date(s), c_date(s) ... I want a file which is in a_date(s) and ends ...
6
votes
4answers
318 views

How to atomically allocate a loop device?

I am writing some shell scripts to handle some disk image stuff, and I need to use loop devices to access some disk images. However, I am not sure how to properly allocate a loop device without ...
2
votes
1answer
34 views

How to detect if DE is Unity or XFCE via shell script?

I have a few configuration scripts that I run everytime I install a fresh version of Ubuntu. Recently, however, I migrated to Xubuntu. I would like to use the same script for both distros, since both ...
4
votes
3answers
242 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 ...
3
votes
4answers
173 views

Shell Scripting: Proper way to check for internet connectivity?

I found scripts that say they check for internet connectivity. Some check the ip address if the interface is connected BUT it does not check for internet connectivity. I found some that uses ping like ...
105
votes
7answers
23k views

Why is it better to use “#!/usr/bin/env NAME” instead of “#!/path/to/NAME” as my shebang?

I notice that some scripts which I have acquired from others have the shebang #!/path/to/NAME while others (using the same tool, NAME) have the shebang #!/usr/bin/env NAME. Both seem to work ...
5
votes
3answers
188 views

Easiest way to find missing quote in a bash a script?

I have a bash script which is currently 700+ lines long. After a particularly long round of editing, it now errors like so: ./run_me.sh: line 693: unexpected EOF while looking for matching `'' ...
0
votes
1answer
29 views

cant run dd command on android device

The main objective is to send a splited file to an android and join it back up with a .sh script, the file is splited to 5MB parts but its total size is unknown (trying to make an universal script), ...
4
votes
4answers
137 views

Move files by date into different directory using CLI

I have a large number of pictures from an old hard drive that I'm trying to organize. If I run ls -l, I notice all of these files have a creation date of 2012 or before. Ideally, I'd like to move ...
2
votes
4answers
79 views

Extract two values from the output of a command

I'm using the following command in a script to get synthetic wifi info: echo "$( iw dev wlp1s0 link | grep '^\s*SSID:\s' | sed -r 's/^\s*SSID:\s//' ) $( iw dev wlp1s0 link | grep ...
2
votes
3answers
47 views

How can I prepend and append to each member of an array?

I have an array: CATEGORIES=(one two three four) I can prepend to each array member using parameter expansion: echo ${CATEGORIES[@]/#/foo } I can append to each array member the same way: echo ...
18
votes
5answers
935 views

How can I propagate my SSH pub key to a list of servers without having to type my password in over and over?

I was recently given username/password access to a list of servers and want to propagate my SSH public key to these servers, so that I can login more easily. So that it's clear: There is not any ...
1
vote
1answer
69 views

Which one works faster - regular operators (such as <,>,=) or using (-lt, -gt, -eq)? and why?

Which one works faster - regular operators (such as <,>,=) or using (-lt, -gt, -eq)? and why?
3
votes
4answers
44 views

How to get the PID of a sub process across to the parent process in a bash shell script?

My shell script is as following: #!/bin/bash ./process1 #It will create a sub process: sub_process1 while [ condition ]; do break done kill -9 process1 and sub_process1 In my script, it will ...
1
vote
1answer
18 views

Script samba password but securely

I want to script the addition on a samba user and the password. I have seen solutions similar to the one here Piping password to smbpasswd echo -ne "$PASS\n$PASS\n" | smbpasswd -a -s $LOGIN but ...
0
votes
1answer
37 views

Test variable in a bash case statement

What I want is simply to do something if the first variable of the script is empty, in a case statement. Unfortunately I spent yet a certain amount of time searching for the solution but didn't find ...
0
votes
2answers
29 views

Timeout function return value

I'm using the timeout function on debian to wait 5 seconds for my script. Works great but the problem I have is that I need a return value. Like 1 for timeout and 0 for no timeout How am I going to ...
3
votes
0answers
40 views

Bash Script — ffmpeg not being invoked as expected

I'm working on a bash script to convert my music library to ogg* but executing the right command is somehow eluding me. This is the line that should accomplish it: ffmpeg -i "${file}" -f flac pipe:1 ...
0
votes
0answers
16 views
0
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3answers
112 views

How to loop through lines in a file which contains * in each line

I have a file that contains about 800 lines. All the lines contains 1 * character in it. I need to loop through the lines in the file so I used the following simple for loop for i in $(cat ...
0
votes
1answer
24 views

PHP script to monitor process and write status to a file

I want to write a php script for monitoring particular process using top command and write into the file. I use top -p pid for monitoring a particular process and also i write a shell script for ...
0
votes
2answers
350 views

Using chown $USER:$USER inside bash script

In a small bash script I'm running I am attempting to chown a new directory that is created. I've added: sudo chown $USER:$USER /var/www/$sitename sudo chmod 775 /var/www/$sitename after the line ...
3
votes
3answers
238 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 ...
1
vote
2answers
33 views

Url Decoding shell script

How can I store the url-decoded string in a variable using shell script #!/bin/sh alias urldecode='python -c "import sys, urllib as ul;print ul.unquote_plus(sys.argv[1])"' ...
4
votes
2answers
2k 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 ...
1
vote
3answers
99 views

How to decode base64 text in xml file in Linux?

I'm new in linux (shell). I need to decode base64 text in xml file using linux shell script. Could you please help me to write linux shell script for decoding the values of those tags where attribute ...
0
votes
1answer
20 views

Help killing off Process for Mem Leak

I am currently building an Android LP kernel, and have some pretty sweet tweaks already running and built into it. I know there are numerous LP memory leaks (i've already got the bootanimation one ...
13
votes
5answers
19k views

Passing named arguments to shell scripts

Is there any easy way to pass (receive) named parameters to a shell script? For example, my_script -p_out '/some/path' -arg_1 '5' And inside my_script.sh receive them as: # I believe this ...
-1
votes
1answer
31 views

Webpage content - search for pattern & save to file

I have a web page, say https://test.salesforce.com. I would like to search for a pattern, e.g. "src" at the beginning of a line in the entire webpage content. If the pattern is found, I need to ...
2
votes
1answer
43 views

How do I properly escape this long su + sed command?

#!/bin/bash wineuser=tom su $wineuser -c "sed -i '$ialias ptgui "wine ~/.wine/drive_c/Program\ Files/PTGui/PTGui.exe\"' /usr/people/$wineuser/config/cshrc.csh" The acutal line inserted to tom's ...
2
votes
1answer
107 views

How can I check if rsync made any changes in bash?

I have a script which uses rsync to sync data in a remote -> local scenario. Immediately after the rsync command is run, a check to see if the error code equals zero or not. If its zero, further ...