cit 500: it fundamentals

CIT 500: IT Fundamentals

Text Processing

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Topics

1. Displaying files: cat, less, od, head, tail2. Creating and appending3. Concatenating files4. Comparing files5. Printing files6. Sorting files7. Searching files and regular expressions8. Sed and awk

Displaying Files

1. cat2. less3. od4. head5. tail

Displaying files: catcat [options] [file1 [file2 … ]]

-e Displays $ at the end of each line.

-n Print line numbers before each line.

-t Displays tabs as ^I and formfeeds as ^L

-v Display nonprintable characters, except for tab, newline, and formfeed.

-vet Combines –v, -e, -t to display all nonprintable characters.

Displaying files: less

less [file1 [file2 … ]]h Displays help.q Quit.space Forward one page.return Forward one line.b Back one page.y Back one line.:n Next file.:p Previous file./ Search file.

Displaying files: odod [options] [file1 [file2 … ]]

-c Also display character values.

-x Display numbers in hexadecimal.

> file /kernel/genunix/kernel/genunix: ELF 32-bit MSB relocatable SPARC> od -c /kernel/genunix0000000 177 E L F 001 002 001 \0 \0 \0 \0 \0 \0 \0 \0 0000020 \0 001 \0 002 \0 \0 \0 001 \0 004 246 230 \0 \0 \00000040 \0 033 ^ ` \0 \0 \0 \0 \0 4 \0 \0 \0 \0 \0 0000060 \0 017 \0 \n 235 343 277 240 310 006 004 244 020

Displaying files: head and tail

Display first/last 10 lines of file.

head [-#] [file1 [file2 … ]]-# Display first # lines.

tail [-#] [file1 [file2 … ]]

-# Display last # lines.

-f If data is appended to file, continue

displaying new lines as they are added.

File Size

Determining File Size– ls –l

wc [options] file-list

CIT 140: Introduction to IT Slide #9

Word count: wcwc [options] target1 [target2, …]

-c Count bytes in file only.

-l Count lines in file only.

-w Count words in file only.

Creating and Appending to Files

Creating files> cat >fileHello worldCtrl-d

Appending to files> cat >> fileHello world line 2Ctrl-d> cat fileHello worldHello world line 2

Concatenating Files

> cat >file1

This is file #1

> cat >file2

This is file #2

> cat file1 file2 >joinedfile

> cat joinedfile

This is file #1

This is file #2

Comparing files: diffdiff [options] oldfile newfile

-b Ignore trailing blanks and treat other strings of blanks as equivalent.

-c Output contextual diff format.

-e Output ed script for converting oldfile to newfile.

-i Ignore case in letter comparisons.

-u Output unified diff format.

diff [options][file1][file2]

Comparing Files with diff

diff Example> diff Fall_Hours Spring_Hours1c1< Hours for Fall 2004---> Hours for Spring 20056a7> 1:00 - 2:00 p.m.9d9< 3:00 - 4:00 p.m.12,13d11< 2:00 - 3:00 p.m.< 4:00 - 4:30 p.m.

uniq [options][+N][input-file][output-file]

> cat sampleThis is a test file for the uniq command.It contains some repeated and some nonrepeated lines.Some of the repeated lines are consecutive, like this.Some of the repeated lines are consecutive, like this.Some of the repeated lines are consecutive, like this.And, some are not consecutive, like the following.Some of the repeated lines are consecutive, like this.The above line, therefore, will not be considered a repeatedline by the uniq command, but this will be considered repeated!line by the uniq command, but this will be considered repeated!

> uniq sampleThis is a test file for the uniq command.It contains some repeated and some nonrepeated lines.Some of the repeated lines are consecutive, like this.And, some are not consecutive, like the following.Some of the repeated lines are consecutive, like this.The above line, therefore, will not be considered a repeatedline by the uniq command, but this will be considered repeated!

Removing Repeated Lines

uniquniq [options] input [output file]

-c Precedes each output line with a count of the number of times the line occurred in the input.

-d Suppresses the writing of lines that are not repeated in the input.

-u Suppresses the writing of lines that are repeated in the input.

Removing Repeated Linesuniq [options][+N][input-file][output-file]

> uniq -c sample

1 This is a test file for the uniq command.

1 It contains some repeated and some nonrepeated lines.

3 Some of the repeated lines are consecutive, like this.

1 And, some are not consecutive, like the following.

1 Some of the repeated lines are consecutive, like this.

1 The above line, therefore, will not be considered a repeated

2 line by the uniq command, but this will be considered repeated!

> uniq -d sample

Some of the repeated lines are consecutive, like this.

line by the uniq command, but this will be considered repeated!

> uniq -d sample out

> cat out

Some of the repeated lines are consecutive, like this.

line by the uniq command, but this will be considered repeated!

Printing Files

Printing FilesPrinting Files

lp [options] file-list

lpr [options] file-list

lpq [options]

Printing Files

Canceling Your Print Jobcancel [options] [printer]

Printing Files

Canceling Your Print Job (Contd)lprm [options][jobID-list][user(s)]

Printing Files

Sorting

Ordering set of items by some criteria.

Systems in which sorting is used include:– Words in a dictionary.– Names of people in a telephone directory.– Numbers.

Sorting: sortsort [-f] [-i] [-k #] [-d] [-l] [-v] files

-d Sort in dictionary order (default.)

-f Ignore case of letters.

-i Ignore non-printable characters.

-k # Sort by field number #

-n Sort in numerical order.

-r Reverse order of sort

-u Do not list duplicate lines in output.

sort Example> cat days.txtSundayMondayTuesdayWednesdayThursdayFridaySaturday> sort days.txtFridayMondaySaturdaySundayThursdayTuesdayWednesday

sort Example> cat days.txtSundayMondayTuesdayWednesdayThursdayFridaySaturday> sort -r days.txtWednesdayTuesdayThursdaySundaySaturdayMondayFriday

sort Example> cat numbers.txt10155715820019> sort numbers.txt10120015571589> sort -n numbers.txt95810120015571

Searching Files: grepgrep [-i] [-l] [-n] [-v] pattern file1 [file2, ...]

Search for pattern in the file arguments.

-i Ignore case of letters in files.

-l Print only the names of files that contain matches.

-n Print line numbers along with matching lines.

-v Print only nonmatching lines.

Simple Searches> grep catt /usr/share/dict/wordscattail...wildcatting> grep -c catt /usr/share/dict/words29> grep –c –v catt /usr/share/dict/words98540> wc –l /usr/share/dict/words 98569 /usr/dict/words> grep –n catt /usr/share/dict/words28762:cattail…97276:wildcatting

Regular Expressions^ Beginning of line$ End of line[a-z] Character range (all lower case)[aeiou] Character range (vowels). Any character* Zero or more of previous pattern{n} Repeat previous match n times{n,m} Repeat previous match n to m timesa|b Match a or b

Regular Expression Searches> egrep ^dogg /usr/share/dict/wordsdogged…doggy’s> egrep dogg$ /usr/share/dict/words> egrep mann$ /usr/share/dict/wordsBertelsmann…Weizmann> egrep ^mann /usr/share/dict/wordsmanna…mannishness's

Regular Expression Searches> egrep 'catt|dogg' /usr/share/dict/wordsboondoggleboondoggled...wildcatting> egrep 'catt|dogg' /usr/share/dict/words | wc –l54> egrep '^(catt|dogg)‘ /usr/share/dict/wordscattail…doggy’s

Character classes> egrep [0-9] /usr/share/dict/words> egrep –c ^xz /usr/share/dict/words0> egrep -c ^[xz] /usr/share/dict/words153> egrep -c [xz]$ /usr/share/dict/words321> egrep -c [aeiou][aeiou][aeiou][aeiou] /usr/dict/words36> egrep [aeiou][aeiou][aeiou][aeiou][aeiou] /usr/share/dict/wordsqueueing> egrep [aeiou]{5} /usr/share/dict/wordsqueueing> egrep -c :[0-9][0-9]: /etc/passwd9> egrep -c ':[0-9]{2,3}:' /etc/passwd18

Extracting Fields: cutcut [-f #] [-d delim] file

Select sections from each line of file.

-f # Select field #.

-d delim Use delim instead of tab to separate fields.

-b # Select specified bytes instead of fields.

Cut Examples> cut -d: -f 1 /etc/passwd | head -5rootdaemonbinsyssync> cut -d: -f 1,3 /etc/passwd | head -5root:0daemon:1bin:2sys:3sync:4> cut -d: -f 1,3-5,7 /etc/passwd | head -5root:0:0:root:/bin/bashdaemon:1:1:daemon:/bin/shbin:2:2:bin:/bin/shsys:3:3:sys:/bin/shsync:4:65534:sync:/bin/sync

Cut Examples> cut -c1-4 /etc/passwd | head -5rootdaembin:sys:sync> cut -d: -f7 /etc/passwd | cut -c1-4 | head -5/bin/bin/bin/bin/bin> cut -d: -f7 /etc/passwd | cut –c6-20 | head -5bashshshshsync

Searching + Extracting: awk

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awk [-F delim] ‘/pattern/ {action}’

Execute awk program on each line of file.

-F delim Use delim to separate fields

Patterns are regular expressions.

Actions are extremely powerful, as awk is a

simple programming language, but we’ll just

use print $#, where # is the field we want to print.

Awk Examples> awk -F: '{print $1}' /etc/passwd|head -5rootdaemonbinsyssync> awk -F: '{print $1, $3}' /etc/passwd|head -5root 0daemon 1bin 2sys 3sync 4> awk -F: '/root/ {print $1, $3}' /etc/passwdroot 0> awk -F: '/bin\/false/ {print $1, $3}' /etc/passwddhcp 101syslog 102klog 103

Stream Editor: sed

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sed [-n] ‘/pattern/action’ files

sed [-n] ‘[line1,line2]s/pat1/pat2/options’ files

Filter and modify (if specified) each line of file.

-n Do not print lines unless action specifies printing.

Patterns are regular expressions.

Actions: p = print matching lines,

d = delete matching lines

s = replace pattern1 with pattern2

Using Sed like Grep > sed -n '/catt/p' /usr/share/dict/wordscattail…wildcatting> sed -n '/catt/p' /usr/share/dict/words | wc -l29> sed '/catt/d' /usr/share/dict/words | wc -l98540> sed -n '/^dogg/p' /usr/share/dict/wordsdogged…doggy’s> sed -n '/dogg$/p' /usr/share/dict/words> sed -n '/mann$/p' /usr/share/dict/wordsBertelsmann…Weizmann

Sed Examples> cat phones.txtOur phone bill for last year was $859,800,513.57.This is our list of phone numbers:859-572-7568859-572-7721859-572-7568859-572-5468859-572-6930859-572-5334859-572-5320859-572-5659859-572-7568859-572-7739859-572-0000859-572-6544859-572-6346859-572-5330859-572-7551859-572-5571859-572-7786859-572-1453859-572-6025859-572-5333

Sed Substitutions> sed 's/859/(513)/' phones.txt | head -5Our phone bill for last year was $(513),800,513.57.This is our list of phone numbers:(513)-572-7568(513)-572-7721(513)-572-7568> sed 's/859-/(513)-/' phones.txt | head -5Our phone bill for last year was $859,800,513.57.This is our list of phone numbers:(513)-572-7568(513)-572-7721(513)-572-7568> sed '3,99s/859/(513)/' phones.txt | head -5Our phone bill for last year was $859,800,513.57.This is our list of phone numbers:(513)-572-7568(513)-572-7721(513)-572-7568

Sed Substitutions> sed 's/[0-9]*-[0-9]*-[0-9]*/Number Redacted/' phones.txt | head -5Our phone bill for last year was $859,800,513.57.This is our list of phone numbers:Number RedactedNumber RedactedNumber Redacted> sed 's/\([0-9]*-[0-9]*-[0-9]*\)/Phone number is \1/' phones.txt | head -5Our phone bill for last year was $859,800,513.57.This is our list of phone numbers:Phone number is 859-572-7568Phone number is 859-572-7721Phone number is 859-572-7568> sed 's/\([0-9]*\)-\([0-9]*\)-\([0-9]*\)/(\1) \2-\3/' phones.txt | head -5Our phone bill for last year was $859,800,513.57.This is our list of phone numbers:(859) 572-7568(859) 572-7721(859) 572-7568

Sed and Awk Applications

Sed

• Double space a file.• DOS to UNIX line endings.• Trim leading spaces.• Delete consecutive blank

lines.• Remove blanks from

begin/end of file.

Awk

• Manage small file db.• Generate reports.• Validate data.• Produce indexes.• Extract fields from UNIX

command output.

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Sed and Awk vs. Ruby and Others

Sed and Awk– Small languages– Cryptic syntax– Best for writing one liners in the shell

Ruby, Python, Perl, etc.– Large languages– Easy syntax– Best for writing longer programs

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References

1. Syed Mansoor Sarwar, Robert Koretsky, Syed Ageel Sarwar, UNIX: The Textbook, 2nd edition, Addison-Wesley, 2004.

2. Nicholas Wells, The Complete Guide to Linux System Administration, Thomson Course Technology, 2005.

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