08 text processing_tools
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grep is used to search for strings and regular expressions in files and outputs. It has options like -i for case-insensitive searching, -v to return non-matching lines, and -r for recursive searching. cut filters out fields or columns delimited by a character like a colon. sort sorts data alphabetically or numerically with options like -r to reverse the sort order. uniq searches for duplicate lines and has options like -c to output a count of occurrences. tr translates characters between two given sets on a character-to-character basis. tail and head print the end or beginning of a file, with options to specify the number of lines.
![cut
• The “cut” command is used to filter out either fields or
columns of text.
• Syntax:
cut [options] [filename(s)]
• Options:
-f’[n]’ : [n] refers to field number(s); the fields must be separated by
a delimiter.
-d’[delimiter]’ : this option defines which character in our string is
the delimiter; if this option is not supplied by the user, the default
will be used (TAB).
# cut -f'6','7' -d':' /etc/passwd | grep user1
/home/user1:/bin/bash](https://image.slidesharecdn.com/08textprocessingtools-130801014816-phpapp02/85/08-text-processing_tools-5-320.jpg)
![sort
• The “sort” command enabled sorting of data in numerical or
alphabetical orders.
• Syntax:
sort [options] [filename(s)]
• Options:
-m – merge already sorted files
-r - reverse sort order
-M – month name sort
-n – numeric sort
-u – unique sort; display only the first match of a repetitive string in
the file, only once.](https://image.slidesharecdn.com/08textprocessingtools-130801014816-phpapp02/85/08-text-processing_tools-6-320.jpg)
![uniq
• The “uniq” command searches for duplicates line of data.
• Syntax:
uniq [options] [filename(s)]
• Options:
-u – show only lines that are not repeated
-d – show only one copy of the duplicate line
-c – output each line with the count of occurrences
-I – case-insensitive](https://image.slidesharecdn.com/08textprocessingtools-130801014816-phpapp02/85/08-text-processing_tools-7-320.jpg)
![tr
• The “tr” command is used to translate characters.
It uses two sets of characters, given as command arguments and converts
them on a char-to-char basis. Is can also:
Converts letter cases; upper to lower and vice-versa.
Recognizes special characters, such as n (newline)
Cannot open files; can only use data from pipes or redirections from
within files.
• Syntax:
tr [options] charter-list1 charter-list2 < [file]
• Options:
-d – delete all characters appearing in “chars1”
-s - replace instances of repeated characters with a single character.
-cd – delete all characters that are NOT in “chars1”](https://image.slidesharecdn.com/08textprocessingtools-130801014816-phpapp02/85/08-text-processing_tools-8-320.jpg)
![tail
• The “tail” command prints the end of a file
• Syntax:
tail [options] [filename(s)]
• Options:
-n+N print the last N lines (default is 10)
-n-N print the entire file starting from line N
-f follow mode. tail will stay active and update on each new line to the
file](https://image.slidesharecdn.com/08textprocessingtools-130801014816-phpapp02/85/08-text-processing_tools-9-320.jpg)
![head
• The “head” command prints the start of a file
• Syntax:
head [options] [filename(s)]
• Options:
-n+N print the first N lines (default is 10)
-n-N print the entire file until the Nth line](https://image.slidesharecdn.com/08textprocessingtools-130801014816-phpapp02/85/08-text-processing_tools-10-320.jpg)
08 text processing_tools
- 2. grep • ‘grep’ is used to search for strings and/or regular-expressions (REGEX) in other commands’ outputs or as a search tool on its own. • In order to search for a string within file, we can use: # grep -i ’user1' /etc/passwd user1:x:500:500::/home/user1:/bin/bash • ‘grep’ will output the entire line in which the string we searched for was found, as seen in the example above.
- 3. grep • grep has many options we can use; some of the common ones are: -i : case-insensitive; do not mind upper or lower case. -v : return anything that is NOT the string we’ve searched for. -r / -R : recursive; search through sub-directories as well. -q : suppress all normal output; useful when checking and evaluating in scripts. • For the full list of options, run: “grep --help” or “man grep”.
- 4. grep • There are two more variants of grep: fgrep – suited for string searches only; the searches are performed faster. egrep – suited for extended regex searches. • grep can also be used as a filter, on the right side of pipes in order to display only specific outputs: # ls -l | grep “kf” -rw-rw-r-- 1 nir test 0 Jul 19 15:11 kfile9
- 5. cut • The “cut” command is used to filter out either fields or columns of text. • Syntax: cut [options] [filename(s)] • Options: -f’[n]’ : [n] refers to field number(s); the fields must be separated by a delimiter. -d’[delimiter]’ : this option defines which character in our string is the delimiter; if this option is not supplied by the user, the default will be used (TAB). # cut -f'6','7' -d':' /etc/passwd | grep user1 /home/user1:/bin/bash
- 6. sort • The “sort” command enabled sorting of data in numerical or alphabetical orders. • Syntax: sort [options] [filename(s)] • Options: -m – merge already sorted files -r - reverse sort order -M – month name sort -n – numeric sort -u – unique sort; display only the first match of a repetitive string in the file, only once.
- 7. uniq • The “uniq” command searches for duplicates line of data. • Syntax: uniq [options] [filename(s)] • Options: -u – show only lines that are not repeated -d – show only one copy of the duplicate line -c – output each line with the count of occurrences -I – case-insensitive
- 8. tr • The “tr” command is used to translate characters. It uses two sets of characters, given as command arguments and converts them on a char-to-char basis. Is can also: Converts letter cases; upper to lower and vice-versa. Recognizes special characters, such as n (newline) Cannot open files; can only use data from pipes or redirections from within files. • Syntax: tr [options] charter-list1 charter-list2 < [file] • Options: -d – delete all characters appearing in “chars1” -s - replace instances of repeated characters with a single character. -cd – delete all characters that are NOT in “chars1”
- 9. tail • The “tail” command prints the end of a file • Syntax: tail [options] [filename(s)] • Options: -n+N print the last N lines (default is 10) -n-N print the entire file starting from line N -f follow mode. tail will stay active and update on each new line to the file
- 10. head • The “head” command prints the start of a file • Syntax: head [options] [filename(s)] • Options: -n+N print the first N lines (default is 10) -n-N print the entire file until the Nth line