bash,variables , variable substitution (what do you call/name this method)?

variable substitution (what do you call/name this method)?


Tag: bash,variables

Say in bash I have:



instead of:

echo $b3 

what kinda of command to have output of "4" ? I tried below but couldn't.

  1. echo $b($(c))

  2. echo $b{!c}

  3. echo $b${c}

  4. echo ${d[$c]}


You can use an indirect reference for that:

$ c=3
$ b3=4
$ d=b$c
$ echo "${!d}"

Although usually instead of indirect references, arrays should be used when possible.


print filenames into scripts in bash

How do you print each name of a file from a directory into a string and make make new scripts? to print each file name for i in `ls new_manifest*`; do echo $i; done but when I try and print the rest of the string with $i like this is...

Extra backslash when storing grep in a value

In a bash script I have: Check="grep -e '"'\(-S mount\)'"' /etc/audit/audit.rules" set -x When you run it it shows it as: CHECK='grep -e '\''\(-S mount\)'\'' /etc/audit/audit.rules' Now it works exactly what I want but I want to understand it. Why is there 2 extra \'s?...

XSLT filePath with document as variable

I try to use a variable in the filePath, but it isn't working: BodyPart filePath="C:\\FileOutEmail\\($vpDocNr).xml" content-type="" content-id="" content-disposition="" multipart-type="" I also tried with the whole path in a variable without results: BodyPart filePath='$bestand' content-type="" content-id="" content-disposition="" multipart-type="" Is this possible, what is the right syntax?...

Call known function (with parameters) in class whose name is defined by string variable

I have a bunch of classes of various names and each has a performLogic function that accepts a number of preset parameters (always the same): public final class DoSomeAction extends SetupAction { public void performLogic(param1, param2... I want a way where I can call it like this: String actionName =...

Bash script using sed acts differently when passing variable

I have a script that I am writing that checks a value and then based on the value modifies it. I am trying to understand why it works this one way and not the other. Based on the google and stackoverflow searches I did, nothing really fits what I am...

Identifying when a file is changed- Bash

So in my bash shell script, I have it running through a for loop. Inside the for loop, I use find "$myarray[i]" >> $tmp to look for a certain directory each time through the loop. Sometimes, it finds the variable in myarray[i] and sometimes it doesn't. When it does find...

bash interactive script pass input

I'm running the following interactive Jar. java -jar script.jar argument-line-here \n Now I'm creating a bash script which runs the jar file. How do I pass the argument line and the conformation "\n" to this interactive script? these are input lines for the script. This question has some answers, expect...

Undefined local variable post

I write this code: <% @user.posts.each do |post| %> <%= render 'post', locals: { post: post, user: @user} %> <% end %> Then in _post.htm.erb I write follow code: <div class="post-title"> <img src="<%= @user.avatar.url%>" class="img-rounded post-image"> <h4 id="post-name"><%= @user.first_name + ' ' [email protected]_name %> </h4> <div id="post-date"><%= post.created_at.strftime('%d %b -...

Run 3 variables at once in a python for loop.

For loop with multiple variables in python 2.7. Hello, I am not certain how to go about this, I have a function that goes to a site and downloads a .csv file. It saves the .csv file in a particular format: name_uniqueID_dataType.csv. here is the code import requests name =...

SQL Multiple LIKE Statements

I'm currently working on a report that shows me all post codes covered by our sales team. Each team covers over 100 post codes. What i would like to do is create a report that brings back the clients within the post code. Currently my code looks like this. SELECT...

How to get value from property in BeanShell (jmeter)

I have got several thread groups. I want to use variable from the first group. In second group this var should be used in BeanShell. So: in first thread group I created BeanShell Assertion with this code: ${__setProperty(erroriden, ${erroriden1})}; In second thread group I have BeanShell pre-processor. If has line...

Bash alias function with predefined argument

I have an alias gl which is an wrapper for git log. Basically like this function gitLog(){ if [ $# -eq 0 ] then git log else git log -n $1 } alias gl=gitLog I want to add an alias which just calls gitLog with an argument like this alias...

How can I use a variable to get an Input$ in Shiny?

I am new to R and I am creating a shiny application to read a csv and filter data. I am reading the csv file, then creating dropdowns with a loop using the column names and the unique values: output$dropdowns <- renderUI({ if (is.null(x())) { return(NULL) } lapply(1:ncol(x()), function(i) {...

How to extract first letters of dashed separated words in a bash variable?

I would like to extract the first letter of dashed separated words value of my bash variable, like this: MY_TEXT=this-is-my-custom-text I would like to create a second variable like this: MY_INITIALS=timct...

Replace [a-z],[a-z] with [a-z], [a-z] and keep the letters

How can I replace [a-z],[a-z] with [a-z], [a-z] and keeping the letters? Input suny stony brook, stony brook,usa. Output suny stony brook, stony brook, usa. What I have tried sed 's/[a-z],[a-z]/[a-z], [a-z]/g' <<< "suny stony brook, stony brook,usa." sed 's/[a-z],[a-z]/, /g' <<< "suny stony brook, stony brook,usa." ...

Matching string inside file and returning result

I've got a few peculiar issues with trying to search for a string inside of a .db file. The way I tried was by using grep, which does apparently find the string(s), although this is the output: $ grep "ext" *.db Binary file enormous.db matches There are a couple problems...

Is there any way of protecting a variable for being modified at runtime in C?

I was wondering if there is any way of protecting a variable for being modified once initialized (something like "constantize" a variable at runtime ). For example: #include <stdio.h> #include <stdlib.h> int main(void) { int v, op; scanf( "%d", &op ); if( op == 0 ) v = 1; else...

Having two arrays in variable php

i've this code, i'm trying to explode my date e.g "04 June 2015" to have the day and the month in other 2 variables, but i have all in a method, with an array, is it possible, my code doesn't work, it writes "Array[0]" why? while ($i < $number) {...

Aggregate failure codes in bash

I've got a script which has multiple stages, and at each stage it's possible to fail, but the script can carry on running. Concretely, I generate some json, and check if the diff is correct. The diff could be wrong, but it doesn't stop the next stage of json being...

shell script for counting replacements

Ten files located in a directory. Each file content has "apple" word. write a bash shell script to replace "apple" with "banana" in all ten files and Print the number of replacements for each file. Have tried in this way but dont know how to get number of replacement. can...

How do I silence the HEAD of a curl request while using the silent flag?

When I run the curl command and direct the data to a file, I get back the content of the site as expected. $ curl "" > file.txt $ head file.txt Top of site ... However, this command shows a progress bar, which I do not want: % Total %...

AWK|BASH, use double FS and ternary operator

Is it possible? I was wondering how to do: Count fields differentiated by comma. Only the obtained first field of the previous step, count words differentiated by space. If there is more than 2 words, print NF, otherwise $0. Input cellular biol immunogenet, rosario escuela estadist, medellin medellin Expected output...

shell script cut from variables

The file is like this aaa&123 bbb&234 ccc&345 aaa&456 aaa$567 bbb&678 I want to output:(contain "aaa" and text after &) 123 456 I want to do in in shell script, Follow code be consider #!/bin/bash raw=$(grep 'aaa' 1.txt) var=$(cut -f2 -d"&" "$raw") echo $var It give me a error like...

Where are the local variables of an Android app stored?

The Dalvik Virtual Machine (DVM) has a register-based architecture, as opposed to the Java Virtual Machine (JVM) which is stack-based. So I assume that the local variables of an Android app are stored in the registers. Am I correct? If not, please correct me. If yes, what kind of memory...

AWK write to new column base on if else of other column

I have a CSV file with columns A,B,C,D. Column D contains values on a scale of 0 to 1. I want to use AWK to write to a new column E base in values in column D. For example: if value in column D <0.7, value in column E =...

Why does `sort file > file` result in an empty file? [duplicate]

This question already has an answer here: bash redirect input from file back into same file 7 answers When you try to sort a file in-place with sort afile > afile you silently end up with afile being an empty file. Why is that? I'd expect either an error...

using sed to replace a line with back slashes in a shell script

I am trying to replace the bottom one of these 2 lines with sed in a file. <rule>out_prefix=orderid ^1\\d\+ updatemtnotif/</rule>\n\ <rule>out_prefix=orderid ^2\\d\+ updatemtnotif/</rule>\n\ And the following command seems to do that when executed as a command at the bash prompt sed -i '[email protected]_prefix=orderid ^2\\\\d\\+ updatemtnotif/@out_prefix=orderid ^2\\\\d\\+ updatemtnotif_fr/@g' /opt/temp/rules.txt however, when...

How do I check whether a file or file directory exist in bash?

I currently have this bash script (which is located in my home directory, i.e., /home/fusion809/ and I am running it as root as it's necessary for the icon copying lines): cd /home/fusion809/Pictures/Icon* declare -a A={Arch,Debian,Fedora,Mageia,Manjaro,OpenSUSE} declare -a B={Adwaita,Faenza,gnome,Humanity} for i in $A; do for j in $B; do if test...

Bash script that removes C source comments

I need to write a bash script which copies all .c files from a directory $2 to another directory $1, but without comments. I only have to remove comments that begin with //, might have tabs/spaces before the comment, but not letters. Also, I need to do it with only...

While loop in bash using variable from txt file

I am new to bash and writing a script to read variables that is stored on each line of a text file (there are thousands of these variables). So I tried to write a script that would read the lines and automatically output the solution to the screen and save...

PHP Define var = one or other (aka: $var=($a||$b);)

Is there a way to define a php variable to be one or the other just like you would do var x = (y||z) in javascript? Get the size of the screen, current web page and browser window. var width = window.innerWidth || document.documentElement.clientWidth || document.body.clientWidth; var height = window.innerHeight...

How to test if a command is a shell reserved word?

I am writing a bash script and I would like to verify if a string is a shell reserved word (like if, for, alias, etc...). How can I can do this?...

how to modify an array value with given index?

I want to modify an array cell, which I can do when I know the cell as a number. However here my cell position is given by $i. pomme[`${i}`]="" I tried without the `` and it doesn't work either? How am I suppose to do it?...

Delphi - Use a string variable's name in assignfile()

Is it possible to use a variable in the assignfile command? Eg. f : Textfile ; sFile : string ; {contains 'MyFile.txt' as content} ... cFileDir = 'C:\Users\User\Desktop\Data Engine\Data\Country' ; ... Assignfile(f, cFileDir + '\' + sFile) ; ... I appreciate your help very much. if it's unclear I'll edit...

Capitalize all files in a directory using Bash

I have a directory called "Theme_1" and I want to capitalize all the filenames starting with "theme". The first letter of every file name is lowercase and I want it to be upcase. I've tried this but all the letters in the filename are upcase, which is not what I...

subtracting from multiple variables at a time

So recently I've ben interested in learning python, and I got the "Think python" last Christmas. Unfortunately I haven't had the time to really get into it because of my exams. Even though I the book was written for python 2 I decided to use python 3.4.3 anyway. This does...

How to append entry the end of a multi-line entry using any of stream editors like sed or awk

I am trying to use a script to append the host name at the end of a multi-line entry of a specific Host_Alias field in sudoers file. The current sudoers file has an entry similar to : Host_Alias srv_linuxestate= \ host10,host12,host13,host1,host50,\ host16,host1,host2,host11,host15,host21,\ host3,host14 My required output would be something like...

Very weird behavior when using “var” keyword in an ajax request

I've been worrying about this for a while and I can't realize what's really happening. Explanation in code comments. There are 2 versions of an application, one of them throws weird results and the second one does the expected work. var id = "test1"; $.post("", {"data": "data"}, function(a) { alert(id);...

Compiler modifying a variable without adressing it

In my program I found that when asssigning a variable to another, modifying the first one, also modifies the second. Example: using System; using System.Collections.Generic; using System.Windows.Forms; namespace Dict_test { public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void TestButton_Click(object sender, EventArgs e) { Dictionary<string,...

How to change svn:externals from bash file non-interactive

I have multi externals need to be set within a file externals.txt and I attempt to change the svn:externals from a bash: svn pe svn:externals svn://hostname/branchname -F extenals.txt But the command throws out an error: svn: E205007: None of the environment variables SVN_EDITOR, VISUAL or EDITOR are set, and no...

Get variable *value* instead of variable itself

Look at this code: <button id="button">Test</button> <button id="button2">Test</button> <script> button = document.getElementById("button"); button2 = document.getElementById("button2"); var x = 5; button.onclick = function() { alert(x); } var x = 10; button2.onclick = function() { alert(x); } </script> When I click on both of the buttons, I get 10 as result. But...

Python: can't access newly defined environment variables

I can't access my env var: import subprocess, os print os.environ.get('PATH') # Works well print os.environ.get('BONSAI') # doesn't work But the env var is well added in my /home/me/.bashrc: BONSAI=/home/me/Utils/bonsai_v3.2 export BONSAI And I can access this env var from a new terminal....

SQL Repeated Condition in Two Tables

I am a beginner to SQL, and I am having trouble getting rid of repeated code. I have a condition "AccountId=20" that I use twice in a SQL query. The SQL looks something like: DELETE FROM Table_A WHERE FunctionId IN (Select FunctionId FROM Table_B WHERE AccountId=20); DELETE FROM Table_B WHERE...

Why can I view some Unix executable files in Mac OS X and not others?

I am on a Macbook Pro on Mac OS X 10.10 (Yosemite). When I go to /usr/bin, git is there as a unix executable file. When I open it up in Sublime Text, all I get is unreadable machine code. However, when I open up a different Unix executable file—in...

Macports switch PHP CLI version

I'm trying to switch my Terminal PHP version to 5.4 because I ran into some issues with Drush while updating my Drupal core. The reason for these issues is my Terminal PHP version is different then my localhost. php -v in Terminal returns PHP 5.5.13 (cli) but my localhost...

linux - running a process and tailing a file simultaneously

I want a run a long task on a remote machine (with python fabric using ssh). It logs to a file on the remote machine. What I want to do is to run that script and tail (actively display) the log file content until the script execution ends. The problem...

Assign and use of a variable in the same subshell

I was doing something very simple like: v=5 echo "$v" and expected it to print 5. However, it does not. The value that was just set is not available for the next command. I recently learnt that "In most shells, each command of a pipeline is executed in a separate...

Bash modify CSV to change a field

I have a very big CSV file (aprox. 10.000 rows and 400 columns) and I need to modify certain columns (like 15, 156, 220) to change format from 20140321132233 to 2014-03-21 13:22:33. All fields that I need to modify are datetime. I saw some examples using awk but for math...

Maya MEL variables declaration and initialization

Is it obligatory in MEL to initialize variables and especially strings when you declare them? I know that it is not necessary to initialize string arrays: string $buffer[]; $buffer[0] = "abc"; But what about strings and other variable types? Is it acceptably: string $str; $str = "abc"; Or should always...