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©Copyright Network Development Group 2013.
Chapter 3: Text Utilities

The cat* command
• The cat command merges two or more files
into a single file:
$cat file1 file2 > file3
• Can also be used to display the contents of a
file to the terminal:
$cat file1
*concatenate

The more & less commands
• While the cat command can be used to
display the contents of a file to the terminal, it
doesn't "pause" the display
• Use the more command to view a file one
page at a time
• The less command uses many of the
navigation keys used by the vi text editor in
addition to ones used with more

The file command
• Only text files should be displayed, not binary
files
• Displaying binary file can cause terminal
corruption
• Either logout or run the reset command to fix
terminal corruption
• To view file contents type, use the file
command:
$file filename

The split command
• The split command will break large files into
smaller files
• Useful for file transfer when large files create
problems
• Syntax:
split [OPTION]...[INPUT [PREFIX]]
• INPUT is a file or stdin

The split command
• By default the new files will be named with a
prefix of x and a suffix of aa, ab, etc.
• For example, the first file would be called xaa,
the second file would be called xab, etc
• The -d option splits files to have a numeric
suffix instead of a default alphabetic suffix
• The file names will start with the PREFIX, if
specified; if not specified, then "x" is used

The nl command
• The nl command will number the lines of its
output
• By default will only number lines that are not
blank
• To number every line use:
$nl -ba

The head command
• The head command views the beginning
of a file or output of another command
• Displays 10 lines by default
• Use -n to specify a different number of
lines to display:
$head –n -30

The tail command
• The tail command views the end of a file
or output of another command
• Displays 10 lines by default
• Use -n to specify a different number of
lines to display
$tail–n -25
• Use -f to "follow" file changes

The paste & join commands
• The paste command merge the lines of one
or more files, line by line, using a tab delimiter
by default
• Use -d to specify a different delimiter
• The join command merges files, matching
the values of fields to determine which lines
to combine
• Use -t to specify a different delimiter

The expand & unexpand commands
• The expand command will convert tab
characters into spaces
• The unexpand command will convert space
characters into tabs
• Useful to make the content of files consistent
• Use -t to specify a tab stop position

The cut command
• The cut command extracts fields of
information from a text file
$head -1 /etc/passwd | cut -d: -f1,5,6,7
root:root:/root:/bin/bash
• Default field separator is space or tab
• Use -d to change field separator

The sort command
• The sort command displays a file sorted on a
specific field of data
• To specify the fields to sort from first to last,
you can use one or more -k options

The sort command
• Use the "n" value to perform numeric sorts
$sort -t',' -k1n os.csv
1970,Unix,Richie
1970,Unix,Thompson
1987,Minix,Tanenbaum
191,Linux,Torvalds

The sort command
• Use the "r" value to reverse sort order
• Use the -u option to remove duplicate lines

The uniq command
• The uniq command removes duplicate lines
from sorted documents
• Use -c to get a count of each line

The fmt command
• The fmt command does very simple text
formatting
• The most common purpose is to format a text
file with a maximum line width
• Use -w option to specify the width of each
line

The pr command
• The pr command prepares a file for printing
by
- breaking the file into "pages“
- displaying header information at the top of
each page
• Use -l to specify lines per page
• Use -d to double space
• Use -o to specify a margin

The od command
• The od command performs an octal dump of
data by default
• Used to display the contents of a file when it
contains non-printable characters

The od command options
Single Option Option with Argument Meaning
-a -t a Named characters, ignoring high
bit
-b -t o1 Octal bytes
-c -t c ASCII characters or backslash
escapes
-d -t u2 Unsigned decimal 2-byte units
-f -t fF Floats
-i -t dI Decimal integers
-l -t dL Decimal longs
-o -t o2 Octal 2 byte units
-s -t d2 Decimal 2 byte units
-x -t x2 Hexadecimal 2 byte units

The tr command
• The tr command can be used to translate
from one set of characters to another
$tr 'a-z' 'A-Z' < alpha-
first.txt.original
A IS FOR APPLE
B IS FOR BEAR
C IS FOR CAT
D IS FOR DOG
E IS FOR ELEPHANT

The sed command
• The stream editor command (sed) can be
used to modify text
$sed 's/Apple/Animal/' alpha-first.txt
A is for Animal
B is for Bear
C is for Cat
D is for Dog
• Use -i to modify the original file

The sed command
• Replaces first occurrence only be default
• Use -g to modify all occurrences
• Use -i to perform case insensitive matches

The sed command
• Use "i" to insert
• Use "a" to append

The sed command
• Use "d" to delete lines
• Use "c" to change lines

The sed command
• Use -e to provide multiple changes

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