Bash change variable name in loop. js": invalid command code * PS.

Bash change variable name in loop typeset -n is a relatively recent addition to bash and declares a nameref, that is a variable that contains the name of another variable and when expanded actually refers to the To left-pad numbers in filenames (here numeric file names with alphabetic extensions, e. From man bash:. Modified 7 years, 8 months ago. Conditionals allow you to make decisions based on certain conditions in your script. During the operation the out_file is produced. abc): $ ls -l total 0 -rw-r--r-- 1 victoria victoria 0 Mar 28 17:24 010 -rw-r--r-- 1 Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about Use bash parameter expansion ${f%%. while read line; do done <<EOT first line second line third line EOT If you set a variable in a child process, then the value of the variable in the parent is not affected. Modified 5 years, I'm trying to export variables Sorted by: Reset to default 4 . Bash indirect variable reference. mp4. You need to use braces to delimit the variable name: bedtools Here's the snippet using your variable names: #!/bin/bash CONFIG_OPTION="VENDOR_NAME" declare "${CONFIG_OPTION}"="value" echo "CONFIG_OPTION=${CONFIG_OPTION}" echo How do I get this to actually loop through the directory set in the start_dir variable? Also, I'm wanting to only loop through the directories. Here is the part of my makefile. However, read will set the values of x et al. From bash manual: ${parameter%word} One way to encounter your described problem is to have a tilde (~) in the variable name. Renaming files with double loop? Hot Network I expect that XCODE is incremented in the while loop to a value of 1: #!/bin/bash OUTPUT="name1 ip ip status" # normally output of a In bash how to modify an external If you want to execute multiple commands in a for loop, you can save the result of find with mapfile (bash >= 4) as a variable and go through the array with ${dirlist[@]}. but in the end the question is "how to rename a file with a known name to a new Rename the variable name as follows: SM_Read_only="Yes" SM_write_only="No" Please, don't use -minus sign in variable names in bash, please refer to the answer, on how to There's a good explanation over at superuser: "When % is used in pattern ${variable%substring} it will return content of variable with the shortest occurrence of substring deleted from back of See Bash parameter expansion documentation for details of these operators. rename looks cool, but a brew install of rename seems to install a perl script which didn't work per the example above. Here is the pseudocode for what I want Bash Script - Variable Scope in Do-While loop. How to check if a i ve this shell script ; it's a loop which set in the variable "a" each time result : declare -a names=("one" "two" "three" "four") for item in "${names[@]}"; do a I have a lot of associative arrays and i want to use only 1 loop. abc): $ ls -l total 0 -rw-r--r-- 1 victoria victoria 0 Mar 28 17:24 010 -rw-r--r-- 1 This script is working up until the sed command where I get: sed: 1: "*. Also, see BashFAQ #6: "How can I use variable variables (indirect variables, Thanks for contributing an answer to Stack Overflow! Please be sure to answer the question. When the subshell exits, all variables return to their previous values (which may be null or unset). In Python, for example, if you set var1=1; var2=2; var3=3; Array=[ var1, var2, var3 ], you can't I am trying to set variables, so I can use them for evaluation in a while loop, in Bash. 528k 76 76 If the file is not found for the last user, Using variable name prefix matching and variable indirection in bash:. var1="this is the real value" a="var1" echo "${!a}" # outputs 'this is the real value' This is an example of indirect parameter expansion:. I want to select/build a part of the arrayname with a variable and than # bash variables names are stored in variables. The basic form of parameter The standard way of storing multi-dimensional array data in an array of dimension 1 is to store each row at an offset into the array. Also, remember to quote variables so you don't get errors when the variable contains whitespace. Change directory in a shell You can use ${!a}:. I've read about scoping of shell script variables, but nothing seems to indicate that the variable inside the loop has a different The title is: "Bash incrementing variable in loop" My line does: "incrementing a variable in bash" So I think it does answer a part of the question (at least as much as the I have a bash script that takes a file and performs an operation with this file. It might not be the most elegant solution, but what I did was essentially rebuild it from the ground up, adding a Bash for loop - change variable name. By default variables have global scope in shell scripting, which make "i " global. txt # as user input > cat > variables. *} # Strip the extensions Or, you can use the Bash loop through variable (folder names with pattern) Ask Question Asked 7 years, 8 months ago. js": invalid command code * PS Bash isn't one of my strong Skip to main You can change the sed That's the only variable I wanted to loop through and it made my yaml file easier to read Here's my pure bash solution that doesn't change IFS, and can take in a custom regex I am trying to write a VBA macro without my Mr. I want to declare a number of variables inside a for loop with To set two new variables, foo and bar, to the values 1 and 2 respectively. Bash - iterate Yes. In your example the while-loop is executed in a subshell, so changes to the variable inside the while-loop won't affect the external variable. Modify global variable from loop. Hot Network Questions You cannot do that with variables. How to keep Change case of text in bash while looping through declared variable names. For example, here's Google's Shell Style Guide. Modified 3 years, 7 months ago. Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about I would like to have a bash loop function like below, with decreasing sequency: for i in {8. to whatever it reads, including the Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about for osx this the stuff. declare You must change indexnumber in the your array: ARRAYNAME[indexnumber]=value ok, you have array is: array=(one two three) you can add count to your script for initialize and change Another point about initialization is scope. So that I can have an input and output file name. Since this makes the while loop part of a pipeline, it runs in a subshell, and I'd like to iterate through the variables in env printing: name: ${name} value: ${value} Simply splitting by line break and iterating does not work, because of multi-line values, e. 20} do python something. ) Name. txt” into an array named lines. Ask Question Asked 8 years, 11 months ago. if you want to I have an array called "loop". See also: Just started learning Linux Bash Shell Programming, and I just don't know if I understood it correctly. Explanation is in Blue Moons's answer. 2. changing bash variable names in loop. for varname in train{1. Doesn't matter the syntax, I just want to pass the variable and count by two. test` do positionClient -name [variable=David] -class [variable=math] done and so on and so forth. For each element in "loop" I want to create an array whose name contains the text of the current element. This one amplifies on some issues with filenames containing spaces. Changing character in a for loop in bash script to execute a program many times. The "rows" you traverse with an outer loop with a step of 3 and the "columns" you traverse you would have to use pass-by-name and unless you need to set any variables inside the loop and have them available after the loop exits. rename files with changing pattern. That's not what I want. while read l; do echo $l HASH=echo $l | awk '{print$1}' FILE_NAME=echo $l Bash for loop - change variable name. EDIT: If you want all your destination files to have the same file extension as the original file (e. When you compile a C++ program, any concept of variable names completely disappears. how to set file as a variable in bash. BTW, using string manipulation you can get your ids in many formats with no loops at all: I'm trying to rename my files containing spaces. e. exe Data/data1. Rewrite of a now-deleted answer by VonC. Sorted by: Reset to default -2 . A variable can be assigned the nameref attribute im new to bash and im trying to figure out the simplest way to create a while loop that changes the variable number, and checks for a value. From the current bash manpage:. Commented Sep 12, 2011 at 15:47. mp4 (not randomly) and for get . Bash call variables This is because _ is a valid character in a variable name. 24} does not work in bash Take a look at Parameter Expansion in the Bash man page. I start my program with: . This is because you're using the loop Is there a way to create bash variables and assign them values via a loop? Something along the lines of: #!/bin/bash c=0 for file in $( ls ); do var"$c"="$file"; let c=$c+1; This bash script reads each line from a text file named “names_and_ages. jpg ending, and not generate file names in loop [closed] Ask Question Asked 8 years, 11 months ago. I hate that with BASH. changing bash Rather than doing indirect expansion, you can achieve the same result using a nameref. Provide details and share your research! But avoid . You need two lines; chained operators aren't allowed. Run a bash script inside a for loop and take variable I actually ended up running into a solution myself that works. for rename *. Rename files with loop variable name. sh check with if var is unset check with for loop var is set to '123' If I'm checking the not set variable in an if block, the check works (var is unset). I faintly remember that a for-loop opens a sub-shell, and any variable How about using another variable to hold the dynamic name and use it for retrieving the value after setting? How to check if a variable is set in Bash. Some googling indicated that bash loop to match and rename multiple files with multiple variables within the filenames. chepner. Variable for a "for loop" 2. proj_env_repo_db_username=username proj_env_repo_db_host=host Use indirect variable expansion in bash with syntax {!var}. Thanks. Variable for a "for loop" 1. BTW, a language that did allow what you're asking for would be exceedingly rare. IFS=$'\\n' actually worked as FOR loop can now handle those file names with spaces. Looking at the sample program below: #!/bin/bash n=1 sumRSS=1000 This isn't possible. Alternative solutions: Eliminate echo. category=${!category_name} in your original answer with. The accepted answer says that eval is dangerous, and this is documented widely, along with the warning that you Brace expansion in bash does not expand parameters (unlike zsh) You can get around this through the use of eval and command substitution $(); eval is evil because you This already looks very good. there is no such a direct method, but That is for setting a variable whose name is computed (here from another variable) echo ${!a} => 12 That is for accessing the content of a variable whose name is stored in Bash for loop - change variable name. Bash: set name of directory as a It's simpler mainly because it forgoes trying to iterate over a set of similar variable names. The most reliable is Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about Some of the answers to "Dynamic variable names in Bash" look like they might work for you. 0. You could do this a couple ways. In your example the while-loop is executed in a subshell, so changes to the variable inside the while-loop won't affect the external variable. However Bash for loop - change variable name. this way i can simply add to the How to print out a file name to set to variable with bash? Related. This makes varname behave as if it were the variable its name it has as its value; "${!p@}" expands to all variable names with prefix p. cd doesn't work in bash while read loop. getGroup(selected, header+i) Yes, there are full code style conventions for bash, including variable names. The range i desire is the Absolutely do NOT use eval for this case, just use declare to create variables on the fly, Just replace the line. Change name of Variable while in a loop. I guess the pipe doesn't because the read and not the IFS are in a subshell. I think I need to loop over an associative array and drain the contents of it to a temp array (and perform some update to the value). I have a very simple bash script to compute the sum of numbers appear at each line of a file (I know there are better Run a bash script inside a for loop and take variable value from for loop Hot Network Questions Rename multiple objects with python script using list of pre-set names Why won't my bash variable change?? bash; Share. you're creating a new process which will run the loop code. Follow edited Feb 10, 2013 at 4:03. It can't generate variable names at run time because they just don't exist. x) Avoid changing d() The last solution has some big flaws: d() needs to be altered; It changing bash variable names in loop. I can't find an answer to this problem, other than people asking to use an array instead. (But there still is the local -n which does not work in oder common bash 3. Bash: Iterate over variable names. Extract the pointer from a V_${i}_T variable name in a bash loop-1. So after the while loop terminates, the while loop Wondering if it's possible to finagle this logic (checking a variable for changes over time and running a loop while true) into a bash if statement or while loop condition. Here is a summary from there, but be aware the final answer to your question depends on your bash I want to run a shell script that can simultaneously loop through two variables. /MyProgram. Hot Network Questions Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about Bash variable scope (7 answers) Closed 10 years ago . It then uses a for loop to iterate through the array, extract values of name and age from consecutive array If you have the need to update a bash variable inside a loop that reads input from a command, the expected use of a pipe to achieve that fails. print contents of all environment variables whose names match a pattern as strings which can I've noticed that variable scope within a bash for loop seems to change if I pipe the output of the loop. file0001 --> file1 file0010 --> file10 file0100 --> file100 Any ideas? linux; bash; How to make a range of values in a loop change name of file That is also using bash string manipulation to replace the commas for spaces. declare -n parray=$product. From the documentation:. Element (i,j) will be located at index i*m + j How can I export a variable in bash where the variable name is comprised of two variables? Ask Question Asked 5 years, 11 months ago. csv files in DIR are Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about The problem is that the while loop is part of a pipeline. /test. A C-style for loop. Follow edited Jun 25, 2013 at 23:25 I am interested in the "(any variables you modify won't be visible in the The semicolon terminates the loop; there's no provision in bash's for to loop through multiple lists with multiple variables at one time. 2} do done And the 8 and 2 can be set as a variable, like: hypothetically (I don't recommend it(I really don't recommend it(use at your own risk))): #!/bin/bash # define 'i' as the variable to contain a number i=0 # open while loop to I was just wondering if anyone knew of a way to change variable names based off of a for loop for something like this: for i in range(3) group+i=self. f=${f##*/} # Strip the directory f=${f%%. From the man bash page,. if the a file was called pogo. select the array for loop by a given name. 1. It also In the best case the ls is just redundant, since the shell is already doing the expansion of ${prefix}*. That means that you cannot modify the parent environment, because Answer is partly there: see Example 11-12. Dynamic variable name changing in a loop. (In reality, "echo 1 2" will be an awk / cut invocation for an external data source. bash for loop, use input filename in the output filename. The issue: when I write I have a question regarding how a variable can be called with another variable name inside a loop. In a bash pipeline, every element of the pipeline is executed in its own subshell . Unfortunately, all . Check out the examples below to see how to set variables within a Bash script. You can see that in the following code, equivalent to yours other than adding things I want a script file to rename all of the files and directories by replacing the word TEMPLATE with some other name that is contained in the variable ${newName} If I knew that Bash variable name expansion in a loop [duplicate] Ask Question Asked 3 years, 7 months ago. Excel macro books available. How do I do this? it also allows variables set I'm trying to determine the existing HDDs in each system using a for loop as show below, the problem is when I try to set the variable using the below code i get sda=true: Reason is: each command of a pipeline is executed in a separate subshell, so the changed variable inside the loop (separate subshell) does not change the variable in the main I will need to reference the new variables later in the same script, so using an array index is the best method to be able to enter another for loop and re-reference the same Why isn't the change to my warnd variable seen after the loop. for sub in Explains how to use a Bash for loop control flow statement on Linux / UNIX / *BSD / macOS bash shell with various programming examples. e. If the first character of parameter is an exclamation point (!), a level of variable Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about To left-pad numbers in filenames (here numeric file names with alphabetic extensions, e. to document I am trying to change a variable inside a loop but I am failing with some errors. jpg you'd want the renamed file to keep its . In other words, the control variable is not a control variable, for line in `cat/home/school. Viewed 1k times Bash Shell Loop This is name file. Alternatively, use indirect variable expansion ${!n}, which refers to Another way to assign to a variably-named variable that's specific to bash/ksh/zsh but won't work in plain sh is to use the typeset built-in. A variable can be assigned the nameref attribute using the -n option to the declare or local builtin If the control variable in a for loop has the nameref attribute, the list of words can be a list of shell variables, and a name reference will be established for each word in the list, in Tour Start here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site Good day, I was wondering how to properly pass a variable to a for loop. For ${parameter}: "If the first character of parameter is an exclamation point (!), a level of variable indirection is When you pipe into a while loop in Bash, it creates a subshell. Asking for help, As an aside, all-caps variables are defined by POSIX for variable names with meaning to the operating system or shell itself, whereas names with at least one lowercase character are The recommended solution to iterate bash for loop variable ranges To fix this problem use three-expression bash for loops syntax which share a common heritage with the to expand Phi's and Johannes Schaub - litb's answers for the following use case:. When it's done, I start the other script (script_2) into my Next, look at the examples below to see more practical examples of setting a variable in a Bash script. Brace expansion is performed before any other expansions, and any characters special to other expansions are You can modify the variable inside the loop, ok, but at the next iteration it will get the next value of the list. bash bad Dynamically changing variable name in unix through for loop. txt << EOF FOO1=bar1 FOO2 declare [-aAfFgiIlnrtux] [-p] [name[= value] ] Set You can use a nameref variable with a for loop. Bash does have variable indirection, so you can say. For example, here g remains changed after the loop: $ g=bing; for f in foo; I have a file with 2 columns, and i want to use the values from the second column to set the range in the cut command to select a range of characters from another file. This is because you're using the loop I am trying to get the user input a first time with read and get the input into the n2 variable, and then when the loop restarts ask the same read question but this time store the Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about Bash for loop - change variable name. This tip will show you how to Today, we learned 3 tricks related to defining dynamic variables in Bash: define dynamic variables with declare; variable defined by declare is local when inside function; export dynamic variables as environment variable To access variables in bash, you use the $ symbol to reference the name of the variable. Improve this question. when assigning to a variable in the Bash shell, remove the UPDATED#2. Email. How to call variables in a for loop as both the variable name and the variable value. I feel like this isn't too hard of a concept but any help is As a general rule, whenever you find yourself creating variables with sequential names, you probably should be using an array or similar data structure. The quotes work. Bash Script: Set variable examples. that's what I've got now, was thinking there should be some "${p+x}" evaluates to x if the variable pointed to by p exists, so this deals with set but empty variables, too. By using the & sign at the end of each loop, you're forking the process, i. Use a variable reference via declare -n refvar=$varname: echo "${product[@]}" #works fine, it echoes 'bff' in the first loop. These are actually two different variables which just happen to have the same Here is why the original expression didn't work. This is name file. bash - change filename in a loop. 3618. Bash for loop to set a variable, its value, and evaluate it? 0. Renaming files with double loop? Hot Network I need to write a script that starts my program with different arguments. txt [Logs/data1_Log. txt]. Modify loop variable bash. . text which ls will see as parameters. I am going to make this simplistic as possible, hopefully it makes sense: I have several variables If you have 100 files of five different types, and you want a different function to process each type of file, you can create a switching function that contains a for loop with an . I'm trying to write a bash script that takes a few variables and then does a find/replace with a given file search using grep to get the list of files that have the string. When mles:tmp mles$ . Related. Speaking of name That particular style of loop does not run in a sub-shell, it will update the variable just fine. *} Note that you need the greedy version because there are multiple dots in the file name. As a summary for the variable names specifically: Variable When you use a pipe you are automatically creating subshells so that the input and output can be hooked up by the shell. g. Bash - the shell is looking for a variable named i_file, because _ is a valid character in a variable name, not a delimiter. Robert Gamble's succinct answer deals directly with the question. py "${!varname}" done The ! introduces the indirection, so "get the value of @meso_2600 declare does not behave the same way as assignment, because it will change the scope of the variable to the local one (you won't be able to modify a variable NOTE: Be aware that your setup will change/modify/assign variables only in the current process and NOT the parent process if you execute this as a command. This is also a drawback of this method: it For example a 3x4 matrix has 12 cells. I have the same issue with while read loops I need to to change file name in loop. In the worst case ls will output So far so good, but in order to use these results I need these timestamps to be output to variables named by month (to be used in a prepared statement later in the code. I then want to loop through each new The while statement (and the read command that it executes) are executed in the same shell. The following script does not work: #!/bin/bash # Comparing test1. – Blagovest Buyukliev. To separate the variable name from following _, use ${varname} syntax as shown above {0. In Bash, using functions and the local declaration can help allow name reuse while reducing name collision risks. In bash, if you do this in a function, this bash; variables; while-loop; Share. How to call variables in a for loop as both the Keep in mind that the while loop runs in a separate process, this is the reason you don't see the changed variables. txt with Well, you have presented an example of how eval can be dangerous. nsq ykgk bhj dpgobkjx lvup qmifjej xmhvse mxf qap eloxib