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MacOS join command

The MacOS join command is used to merge lines of two sorted files based on a common field. By default, it uses the first field to join the lines. It can be particularly useful for combining data from different sources into a single file. The command requires the input files to be sorted in ascending order based on the field used for joining. The join command also provides options to specify the input field separators and the output field separators. Additionally, it allows for customizing the fields to be displayed in the output.

join Syntax:

Terminal window
join [OPTION]... FILE1 FILE2

Options:

OptionDescription
-a FILEalso print unpairable lines from FILE
-e EMPTYreplace missing input fields with EMPTY
-iignore differences in case when comparing fields
-j FIELDequivalent to ‘-1 FIELD -2 FIELD’
-o FORMATobey FORMAT while constructing output line
-t CHARuse CHAR as input and output field separator

Parameters:

ParameterDescription
FILE1the first file to be joined
FILE2the second file to be joined

Join Two Files by a Common Field

Terminal window
join file1.txt file2.txt

Merges two files based on a common field and displays the result.

Join Files with Different Field Delimiters

Terminal window
join -t',' file1.csv file2.csv

Joins two CSV files using a comma as the field delimiter.

Display Unmatched Lines from Files

Terminal window
join -v 1 file1.txt file2.txt

Shows the lines from file1.txt that do not have a match in file2.txt.

Ignore Case Sensitivity when Joining Files

Terminal window
join -i file1.txt file2.txt

Performs a case-insensitive join operation on two files.

## join Usage:
{EXAMPLES}
:::tip
When using the join command in MacOS, make sure to understand the differences between the options available and how they affect the output. Additionally, ensure that the files you are attempting to join are properly sorted and have a common field for joining.
:::


### How do I use join in MacOS?
To use the join command in MacOS, execute the following command:
```bash
join <file1> <file2>

What is the purpose of the join command in MacOS?

The join command in MacOS is used to combine lines from two files based on a common field.

How can I specify the field for joining in the join command on MacOS?

You can specify the field for joining by using the -1 and -2 options followed by the field number in each file. For example:

Terminal window
join -1 2 -2 1 file1.txt file2.txt

How do I only display the lines that have matching fields in both files using the join command in MacOS?

To display only the lines that have matching fields in both files, you can use the -m option. For example:

Terminal window
join -m file1.txt file2.txt

Can I change the output field separator in the join command on MacOS?

Yes, you can change the output field separator using the -t option followed by the desired separator. For example, to use a comma as the separator:

Terminal window
join -t, file1.txt file2.txt

How do I display unmatched lines from the first file in the join command on MacOS?

To display unmatched lines from the first file, you can use the -a 1 option. For example:

Terminal window
join -a 1 file1.txt file2.txt

How do I ignore case sensitivity when joining files in MacOS using the join command?

To ignore case sensitivity, you can use the -i option. For example:

Terminal window
join -i file1.txt file2.txt

Applications of the join command

  • Merging two sorted text files based on a common field
  • Combining data from two files with a common key field
  • Performing relational database operations on text files
  • Comparing similar data sets in two files