How to use the command unexpand (with examples)
Unexpand is a command-line utility that converts spaces to tabs. It is part of the GNU Core Utilities package and provides several options to control its behavior. This article will illustrate each of the following use cases of the unexpand command.
Use case 1: Convert blanks in each file to tabs, writing to stdout
Code:
unexpand path/to/file
Motivation: In certain scenarios, files may have been formatted using spaces instead of tabs. This can be problematic, especially if there are inconsistencies in indentation styles. By using the unexpand command, we can convert the spaces to tabs, making the formatting consistent and more manageable.
Explanation: The command unexpand path/to/file takes a file path as an argument and converts the blanks (spaces) in that file to tabs. The output is written to stdout, which can be redirected to a file if needed.
Example output:
This is a line with spaces.
This is another line with spaces.
Use case 2: Convert blanks to tabs, reading from stdout
Code:
unexpand
Motivation: This use case is useful when we want to convert spaces to tabs directly from the content available in the command-line input or when the content is piped from another command. It eliminates the need to write the content to a file first.
Explanation: The command unexpand without any arguments reads the input from stdin (standard input). This means that we can provide the content directly in the command-line or pipe it from another command. The blanks (spaces) in the input are converted to tabs, and the output is displayed on stdout.
Example output:
This is a line with spaces.
This is another line with spaces.
Use case 3: Convert all blanks, instead of just initial blanks
Code:
unexpand -a path/to/file
Motivation: By default, unexpand only converts the initial blanks (spaces) to tabs. However, there may be situations where we want to convert all the blanks in a file or content to tabs.
Explanation: The command unexpand -a path/to/file takes the -a option which instructs unexpand to convert all blanks instead of just the initial ones. The file specified by path/to/file is processed, and the output with converted tabs is written to stdout.
Example output:
This is a line with spaces.
This is another line with spaces.
Use case 4: Convert only leading sequences of blanks (overrides -a)
Code:
unexpand --first-only path/to/file
Motivation: Sometimes, we may want to convert only the leading sequences of blanks to tabs while leaving the subsequent ones unchanged. This is useful when formatting code or text documents where indentation is crucial.
Explanation: The command unexpand --first-only path/to/file uses the --first-only option to instruct unexpand to convert only the leading sequences of blanks. This option overrides the -a option and ensures that only the initial blanks are converted. The output with converted tabs is written to stdout.
Example output:
This is a line with spaces.
This is another line with spaces.
Use case 5: Have tabs a certain number of characters apart, not 8 (enables -a)
Code:
unexpand -t number path/to/file
Motivation: By default, unexpand assumes a tab width of 8 characters. However, in certain cases, we may want the tabs to be placed a specific number of characters apart. This can be useful when working with code or aligning content in a specific manner.
Explanation: The command unexpand -t number path/to/file specifies the -t (tabstop) option followed by the desired number of characters between the tabs. This option also enables the -a option, making unexpand convert all blanks instead of just the initial ones. The file specified by path/to/file is processed, and the output with converted tabs is written to stdout.
Example output:
This is a line with spaces.
This is another line with spaces.
Conclusion:
The unexpand command is a handy utility for converting spaces to tabs. With its various options, it provides flexibility in converting blanks based on specific requirements. Whether it is converting blanks in a file, reading from stdin, or modifying the behavior of the conversion, unexpand offers a versatile solution.
