Text file manipulation commands
Cat
First command is cat
. cat writes the contents of a file to the screen.
machine@machine:~ cat exemplo
Red
yellow
brown
black
white
purple
blue
On the cat, we have the -b
option that numbers the lines that are not blank.
machine@machine:~ cat exemplo -b
1 Red
2 yellow
3 brown
4 black
5 white
6 purple
7 blue
Main flags of cat:
-
-b
numbers all non-blank lines. -
-n
numbers all lines, even blank ones. -
-a
show special characters and tabs.
Another cat-like command is tac
. They read the contents of a file backwards.
machine@machine:~ tac exemplo
blue
purple
white
black
brown
yellow
Red
Tail
tail shows the last lines of a file.
tail <file.txt>
flags:
-
-n5
show the last 5 lines of the file -
-n10
lasts ten lines.
In this flag above you can define the number of lines you would like to see, just change it.
Head
The head command displays the first 5 lines of a file.
flags:
-
-n5
show the first 5 lines of the file -
-n10
First ten lines. -
-c10
Displays the first ten characters of the file
Wc
wc counts the number of characters, words, lines and bytes in a file.
wc <file.txt>
flags:
-
-l
specifies number of lines -
-w
specifies number of words -
-m
specifies number of characters -
-c
specifies number of bytes
Sort
The use of sort is to sort the contents of a file.
sort <file.txt>
With the -r
option, reverse order is also possible.
Uniq
uniq writes to output without repeating words from a file
-
-u
show lines that have not been repeated -
-d
show lines that have been repeated -
-c
counts the number of repeated lines
OBS: To be able to use uniq
it must be used together with sort
before being able to sort the file's contents.
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