awk command line variable assignment

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set multiple variables from one awk command?

This is a very common script:

However I dont like this, especially when there are more fields to parse. I guess there should be a better way like:

(var1,var2)=`echo ${teststr} | awk '{print $1 $2}' (in my imagination)

Is that so? Thanks for help to improve effeciency and save some CPU power.

• 2 read -r a b < <(awk '{print $1, $2}' <<< "hello world") –  user12007102 Commented Oct 15, 2021 at 21:54

4 Answers 4

This might work for you:

Will output:

• 1 Thanks to remind me for bash arries. This is the solution. One can also write like this: var=( echo ${blabla} | awk -F"_" '{print $1 " " $3}' )... –  X.M. Commented Mar 2, 2012 at 8:28
• Nice! Use of parentheses is key. –  Max MacLeod Commented Sep 28, 2023 at 13:36

Yes, you can, but the best practice is to use the awk way to pass variables to awk .

Example using shell script variables

Example using environmental variables

It's possible to use script and environmental variables at the same time

You may find bash tricks to circumvent the awk way to do it, but it's not safe.

Explanation and more examples

Awk works this way, because it's a programming language by itself and has it's own way to use variables 'inside' awk statements.

By ' inside ' i mean the part between the single quotes .

Let's see an example, where we turn off DHCP in a config file, all done using variables in a shell script. I'm going to explain the last line of code.

The script isn't optimal, it's main purpose is to use script variables. Explaining how the script does its job is out of scope of this answer, the focus is on explaining the use of variables.

Let's break this last line up to pieces for explanation.

awk -v awkDHCP_LINE="$DHCP_LINE" -v awkSPACES="$SPACES"

This part above assigns the value of DHCP_LINE script variable to the awkDHCP_LINE awk variable and the the value of SPACES script variable to the awkSPACES awk variable.

Please note, that the SPACES variable is passed to awk for the sake of showing how to pass multiple variables only; the awk command doesn't process it.

'FNR==awkDHCP_LINE {sub("dhcp4: yes", "dhcp4: no")}'

This one above is the ' inside ' part of awk where the variable(s) passed to awk can be used.

$CONFIG_FILE

This part is outside awk, a generic script variable is used to specify the file that should be processed.

I hope this clears things a bit :)

Note: if you have lots of variables to pass, the solution provided by @potong may prove a better approach depending on your use case.

• 1 Is this answer about how to pass variables in to awk? The question is about how to assign values from the output of awk to bash variables. –  Jim Holmes Commented May 3, 2023 at 11:29

You can also use shell set builtin to place whitespace seperated (or more accurately, IFS seperated) into the variables $1 , $2 and so on:

Bash has Array Support, We just need to supply values dynamically :)

Bash Array Documentation : http://tldp.org/LDP/abs/html/arrays.html

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Previous: Using Variables in a Program , Up: Variables   [ Contents ][ Index ]

6.1.3.2 Assigning Variables on the Command Line ¶

Any awk variable can be set by including a variable assignment among the arguments on the command line when awk is invoked (see Other Command-Line Arguments ). Such an assignment has the following form:

With it, a variable is set either at the beginning of the awk run or in between input files. When the assignment is preceded with the -v option, as in the following:

the variable is set at the very beginning, even before the BEGIN rules execute. The -v option and its assignment must precede all the file name arguments, as well as the program text. (See Command-Line Options for more information about the -v option.) Otherwise, the variable assignment is performed at a time determined by its position among the input file arguments—after the processing of the preceding input file argument. For example:

prints the value of field number n for all input records. Before the first file is read, the command line sets the variable n equal to four. This causes the fourth field to be printed in lines from inventory-shipped . After the first file has finished, but before the second file is started, n is set to two, so that the second field is printed in lines from mail-list :

Command-line arguments are made available for explicit examination by the awk program in the ARGV array (see Using ARGC and ARGV ). awk processes the values of command-line assignments for escape sequences (see Escape Sequences ). (d.c.)

Normally, variables assigned on the command line (with or without the -v option) are treated as strings. When such variables are used as numbers, awk ’s normal automatic conversion of strings to numbers takes place, and everything “just works.”

However, gawk supports variables whose types are “regexp”. You can assign variables of this type using the following syntax:

Strongly typed regexps are an advanced feature (see Strongly Typed Regexp Constants ). We mention them here only for completeness.

• Getting started with awk
• Built-in functions
• Built-in Variables
• Patterns and Actions
• Row Manipulation
• String manipulation functions
• Two-file processing
• Useful one-liners - calculating average from a CSV etc
• Assignment Arguments
• Command-line variable assignment
• Local variables
• Passing parameters to a program using the -v option

awk Variables Command-line variable assignment

Fastest entity framework extensions.

To assign variables from the command-line, -v can be used:

Note that there are no spaces around the equal sign.

This allows to use shell variables:

Also, this allows to set built-in variables that control awk :

See an example with FS (field separator):

Or with OFS (output field separator):

Got any awk Question?

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