join command joins lines of two files on a common field.
Syntax:
# join [OPTION]... FILE1 FILE2
For each pair of input lines with identical join fields, write a line to standard output. The default join field is the first, delimited by whitespace. When FILE1 or FILE2 (not both) is -, read standard input.
join Command Examples
1. To join and show the common lines from given input files:
# join file1.txt file2.txt
2. To print the unpairable lines from specified file:
# join -a 1 # join -a 2
3. To replace the missing fields with empty:
# join -e EMPTY
4. To ignore the case difference when comparing:
# join -i file1.txt file2.txt # join --ignore-case file1.txt file2.txt
5. To obey format while constructing output:
# join -o FORMAT file1.txt file2.txt
6. To use the CHAR as input and output field separator:
# join -r CHAR file1.txt file2.txt
7. To print unpairable and suppress joined:
# join -v 1 file1.txt file2.txt
8. To check the input is sorted:
# join --check-order file1.txt file2.txt
9. To not to check the input is sorted:
# join --nocheck-order file1.txt file2.txt
10. To display the help and exit:
# join --help
11. To get the version info:
# join --version