Text Processing

Text processing is an essential skill when working with the command line. This section covers the basic commands for searching, filtering, and manipulating text.

wc

wc is used to print newline, word, and byte counts for each file.

wc file.txt

Here are some useful flags you can use with wc:

Flag	Description
`-l`	Print the newline counts.
`-w`	Print the word counts.
`-c`	Print the byte counts.

head and tail

head and tail are used to output the first or last part of files.

head file.txt
tail file.txt

Here are some useful flags you can use with tail:

Flag	Description
`-n`	Number of lines to show.
`-f`	Follow the file (tail only).

grep

grep is used to search for patterns in files.

grep "pattern" file.txt

Here are some useful flags you can use with grep:

Flag	Description
`-i`	Ignore case.
`-r`	Recursively search directories.
`-l`	List filenames only.
`-n`	Show line numbers.

awk

awk is a powerful text processing language used for pattern scanning and processing.

awk '{print $1}' file.txt

Here we print the first column of file.txt.

Examples

Print specific columns:
```
awk '{print $1, $3}' file.txt
```
Filter based on pattern:
```
awk '/pattern/ {print $0}' file.txt
```

sed

sed is a stream editor used for filtering and transforming text.

sed 's/old/new/' file.txt

Examples

Replace all occurrences of a string:
```
sed 's/old/new/g' file.txt
```
Delete lines containing a pattern:
```
sed '/pattern/d' file.txt
```

cut

cut is used to remove sections from each line of files.

cut -d' ' -f1 file.txt

Examples

Extract specific fields:
```
cut -f1,3 file.txt
```

sort

sort is used to sort lines of text files. By default, it sorts alphabetically.

sort file.txt

Here are some useful flags you can use with sort:

Flag	Description
`-r`	Reverse order.
`-n`	Numerical sort.
`-u`	Print unique lines.

uniq

uniq is used to report or omit repeated lines.

sort file.txt | uniq

Here are some useful flags you can use with uniq:

Flag	Description
`-c`	Count occurrences.
`-d`	Only show duplicate lines.

Next Step

Now that you know how to perform text processing, check out the next section on Process Management to learn how to manage running processes in Bash.

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