cut / paste / join

cut [options] [file...]
paste [options] [file...]
join [options] file1 file2

Command / Option	Description
cut -d delimiter -f field	Splits fields by the delimiter and extracts the specified field number.
cut -f 1,3	Extracts the 1st and 3rd fields.
cut -f 1-3	Extracts fields 1 through 3.
cut -c 1-5	Extracts characters 1 through 5 from each line.
paste file1 file2	Merges corresponding lines from two files, separated by a tab.
paste -d ',' file1 file2	Merges lines using the specified delimiter.
paste -s file	Joins all lines of a file into a single tab-separated line.
join file1 file2	Performs an inner join using the first column of each file as the key (files must be pre-sorted).
join -1 N -2 M file1 file2	Joins using column N of file1 and column M of file2 as the key.
join -a 1 file1 file2	Also outputs unmatched lines from file1 (left outer join).

The following files are used in the examples below.

data.csv

alice,30,Tokyo,engineer
bob,25,Osaka,designer
charlie,35,Nagoya,manager

names.txt

alice
bob
charlie

scores.txt

85
92
78

users.txt (sorted by ID)

001 alice
002 bob
003 charlie

roles.txt (sorted by ID)

001 engineer
002 designer
003 manager

Use cut -d -f to specify a delimiter and field number to extract a column.

cut -d',' -f1,3 data.csv
alice,Tokyo
bob,Osaka
charlie,Nagoya

Use cut -f 1-2 to extract a range of fields.

cut -d',' -f1-2 data.csv
alice,30
bob,25
charlie,35

Use cut -c to extract characters by position.

cut -c1-5 data.csv
alice
bob,2
charl

Use paste to merge two files side by side (tab-separated).

paste names.txt scores.txt
alice	85
bob	92
charlie	78

Use paste -d to specify a custom delimiter.

paste -d',' names.txt scores.txt
alice,85
bob,92
charlie,78

Use paste -s to join all lines of a file into a single line.

paste -s names.txt
alice	bob	charlie

Use join to combine two files based on a shared field (files must be sorted in advance).

join users.txt roles.txt
001 alice engineer
002 bob designer
003 charlie manager

'$ cut' is convenient for simple field extraction, but it cannot handle cases where a field contains the delimiter character (such as quoted CSV). For more complex cases like these, use awk.

For counting or sorting fields, see also sort.