tty, wc, uniq, split, join, cut, paste and more

Different ways to “go home”

cd

cd ~

cd $HOME

cd /home/username

tty

show which is your virtual terminal:

tty

Go to virtual terminal 1:

Ctrl + Alt + F1

Go to virtual terminal 2 or return to GUI:

Ctrl + Alt + F2 to go to tty2

To go to tty 3, and so on.

F3 to go to tty3, and so on.

You can go from a virtual terminal (tty) to a new graphical session by typing:

sudo startx

help

Help provides information on commands built into the Bash shell.

Up Arrow key; press Enter

Execute the last command.

cat .bash_history

It won't display the same as the history command because part of this is in memory.

wc

Lines count, word count, bytes count in a file.

wc /etc/passwd
36 89 2283 /etc/passwd

uniq

Only repeated lines that are next to each other.

nl

Number lines (it doesn't number a blank line):

md5sum, sha256sum, sha512sum

Check if a particular file is corrupted:

split

It is used to break a file into smaller pieces. The -l switch specifies that the split should happen after every designated number of lines.

join

It is used to join lines of two files based on a common field (like a database join). It requires that both input files be sorted on the join field before execution. join matches lines from two files based on a shared field — usually the first field by default.

Example

file1 (id and name):

1 apple

2 banana

3 cherry

file2 (id and color):

1 red

2 yellow

3 dark_red

Both files share field 1 (the id: 1, 2, 3) — that's the common field.

join file1 file2

Output:

1 apple red

2 banana yellow

3 cherry dark_red

If your files aren't sorted, sort them first:

sort file1 -o file1

sort file2 -o file2

join file1 file2

Example with a delimiter, similar to something you might see combining /etc/passwd fields with another file:

join -t: -1 1 -2 1 file_a.txt file_b.txt

Let's extend the same example with unmatched lines, since that's the trickier part.

file1:

1 apple

2 banana

4 date

file2:

1 red

2 yellow

3 dark_red

Notice: 4 date only exists in file1, and 3 dark_red only exists in file2.

Plain join (default = inner join)

join file1 file2

Output:

1 apple red

2 banana yellow

Only the matching keys (1 and 2) show up. The unmatched lines (3 and 4) are silently dropped.

-a to keep unmatched lines

-a 1 says "also include unpaired lines from file1":

join -a 1 file1 file2

Output:

1 apple red

2 banana yellow

4 date

cut

Extract a certain field using the delimiter ':' for the file /etc/passwd

cut -d : -f 7 /etc/passwd

extract the first 10 characters of the file /etc/passwd

cut -c1-10 /etc/passwd

paste

To join 2 files side by side.

Contact

Email

hello@unixtips.eu

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