Other Utilities

1
Other Utilities The Shell

• Head, tail
• Sort, uniq
• Diff, lp, grep, file
• Tr, sed
• Types of Shell
• Redirection
• Piping
• Command Grouping

2
head

• Displays the first ten lines of a file
• cal 2001 gt lost-days
• head lost-days
• Pass a number to head to ask for the number of
  lines you want
• head 6 lost-days
• head 8 lost-days

3
tail

• Similar to head, but displays the last ten lines
  of a file
• tail lost-days
• tail 2 lost-days
• tail 14 lost-days

4
sort

• Displays the contents of a file in order by lines
• sort myfile
• head 20 /etc/passwd gt mypasswd
• cat mypasswd
• sort mypasswd

5
uniq

• Displays a file, skipping adjacent
  duplicatelines.
• cat myfile ltEntergt
• John
• Tom
• Tom
• uniq myfile ltEntergt
• John
• Tom

6
diff

• Compares two files and displays a list of
  differences between them
• cat color1
• red
• blue
• green
• yellow
• cat color2
• red
• blue
• green
• diff color1 color2
• 4d3
• lt yellow

7
lp

• To print a file
• On system V lp report
• On BSD lpr report
• on a printer named mailroom
• lpr Pmailroom report
• To see the printer jobs in queue
• lpq
• To remove a job number 86
• lprm 86
• To send more than one file
• lpr Pmailroom file1 file2

8
grep

• Global Regular Expression Print
• Searches through the file to see if it contains a
  particular string
• who gt users_on
• grep ce144f01 users_on
• Or
• grep LOGNAME users_on
• grep USER users_on

9
file

• Classifies files according to their contents
• file f1
• f1 empty
• file users_on
• users_on ascii text
• file inform
• inform commands text

10
tr

• Translates characters into other characters
• tr 1 a lt myfile
• Each instance of 1 in myfile is located by tr
  and changed into a
• tr 123 abc lt myfile
• 1 ? a
• 2 ? b
• 3 ? c
• tr a-z A-Z lt myfile
• Translates all lower case to uppercase

11
sed

• Stream Editor
• Sed works on the lines of a file one at a time to
  change the instance of the target
• cat caffeine
• coffee coffee
• 2002 coffee coffee
• coke coke
• tea tea
• sed s/coffee/milk/ coffeine
• sed s/coffee/milk/g caffeine
• sed /2002/s/coffee/milk/g coffeine

12
Types of Shell

• Shell the program that waits for you to type a
  command, and then executes it.
• Two general groups

13
Shells Connection ability

• Technical Terms
• Stdin ( standard input)
• Defaultkeyboard
• 2. Stdout(standard output)
• Defaultscreen
• 3. Stderr(standard error)
• Defaultscreen

14
Redirection

• stdout gt ( 1gt )
• send output to a file
• date gt myfile
• stderr 2gt
• send error to a file
• cat myfile 2gt /dev/null
• stdin lt
• take input from a file
• cat lt myfile gt newfile

15
Redirection Interpretation

• Utility gt filename
• (Shell connects output of utility to filename.)
• Utility 2gt filename
• (Shell connects error-output of utility to
  filename.)
• Utility lt filename
• (connects filename to input of utility.)

16
Standard Error

• The error eg not found message appeared on
  your terminal is actually being written to
  standard error not standard output.Example
• ls xx gt filename
• xx not found
• so you still get the message on the terminal.
• To redirect std error to a file, use 2gt
• ls xx 2gt filename

17
Task 1

• Explain what each of the following commands do?
• Sort
• Who gt temp
• Sort temp gt temp2
• Sort temp1
• Sort lt temp2
• Sort lt temp2 gt temp1
• Mailx John lt myletter

18
Appending

• Caution with Redirecting output
• Use gtgt appending instead
• Eg, cat file1 gtgt majorfile

19
Pipes ( )

• Send the stdout of one command to another command
  as stdin
• who sort
• who sort more

20
tee

• The tee utility copies std input to std output
  and to one or more files you specify.
• Who tee whofile

21
Task 2

• What do the following commands do?
• Who sort gt loggers
• Who wc l
• Who grep yourusername
• Who grep USER
• Who grep LOGNAME
• Who tee whofile grep John
• cat numberfile tr 1234 abcd