Introduction to UNIX

1
Introduction to UNIX

• F. Using C Shell Features

2
Using C Shell Features

• Performance Objectives
• 1. Use History to recall/repeat commands
  (history, !, !!)
• 2. Edit a command line using the replace
  function()
• 3. Edit a command line using the substitution
  method (s)
• 4. Identify the concept of STDIN/STDOUT/STDERR
• 5. Redirect data Input and Output (gt, lt)
• 6. Append results of a command to existing files
  (gtgt, gtgt)
• 7. Use Pipes to link command data ()
• 8. Construct simple aliases (alias)
• 9. Recognize three basic error messages

3
Shell Initialization and Termination

• Activities
• Reads .cshrc from home directory when new C
  shell started.
• Reads .login when initiated as a login shell.
• Reads .logout when shell terminated (if the login
  shell)
• Operates in either interactive or non-interactive
  (batch) mode.

4
Built-in Commands

• C Shell contains built-in commands
• alias fg/bg echo history
  ignoreeof
• jobs kill noclobber noglob
  set
• setenv source stop suspend
  umask
• unalias
• The man page for csh is very long (about 100
  screens).
• Use the man search feature (/keyword).

5
The History Mechanism

• Command Line Editing Allows you to
• rerun any command in the history buffer, and
• change/correct commands in the history buffer.
• To set up a history list
• set history15 (.cshrc)
• To display the last n commands.
• host history
• 1 ls -l
• 2 cd ths
• 3 history

6
Command Line Editing

• To make a new simpler command
• host alias hb history
• Note the following
• host cd unix/class/handouts/larn
• unix/class/handouts/larn No such file or
  directory
• host larlear
• cd unix/class/handouts/learn

7
Command Line Editing

• A display of the history buffer reveals
• host history
• 2 cd ths
• 3 history
• 4 cd unix/class/handouts/larn
• 5 cd unix/class/handouts/learn
• 6 history
• To recall a previous command
• host !cd
• host !5

8
Command Line Editing

• You can list the last n commands from the history
  buffer
• host history 6
• 4 cd unix/class/handouts/larn
• 5 cd unix/class/handouts/learn
• 6 history
• 7 cat /home/ths/class0/basics/history/congrats
• 8 cat /etc/motd
• 9 history
• To rerun the correct cd command - !5 or !cd

9
Command Line Editing

• Substitution changes any previous command
• host !7s/0/1
• cat /home/ths/sunclass1/basics/history/cong
  rats
• History list should be similar to the following
• 7 cat /home/ths/sunclass0/basics/history/congrat
  s
• 8 cat /home/ths/sunclass1/basics/history/congrat
  s
• 9 history
• 10 cat /home/ths/sunclass1/basics/history/congrats
  
• 11 history

10
Redirecting Input/Output

• The 3 UNIX standard files are, the terminal.
• STDIN (keyboard)
• STDOUT (display)
• STDERR (display)
• To redirect output to another file, use
• Greater-than gt symbol to redirect STDOUT
• Less-than lt symbol to redirect STDIN
• Ampersand symbol to redirect STDERR

11
Redirecting Input/Output

• Examples
• host cat filea gt fileb (redirect
  creates fileb)
• host cat filec gtgt fileb (appends to
  fileb)
• host cat filed gt e.file (error msgs to
  e.file)
• host cat filex gtgt e.file (append error to
  e.file)
• host mail -s sub address lt file (get input
  from file)

12
Use of Pipes -

• Special symbol
• command options command options ...
• Problem
• How many processes are running on your machine?
• The command ps -ax will show all processes on a
  machine.

13
Using Pipes (Cont)

• But you must count each line on the screen
• ted ps -ax
• PID TT STAT TIME COMMAND
• 0 ? D 216 swapper
• 1 ? IW 000 /sbin/init -
• 2 ? D 012 pagedaemon
• 55 ? IW 259 portmap
• 60 ? IW 000 ypbind
• 62 ? IW 000 keyserv
• 73 ? S 157 (biod)
• 74 ? S 157 (biod)
• 75 ? S 157 (biod)
• 76 ? S 156 (biod)
• 87 ? IW 003 syslogd
• 95 ? IW 000 rpc.statd
• 97 ? IW 000 rpc.lockd
• 101 ? IW 1101 automount
• 104 ? S 041 screenblank
• 109 ? S 2021 update

14
Use of Pipes - (Cont)

• There are several solutions to this problem
• Solution 1
• host ps -ax gt psfile
• host wc -l psfile
• Note the number of processes
• Solution 2
• host ps -ax wc -l
• Note the number of processes
• Why is there a difference of one process?

15
Using Filters with Pipes

• Lists are often difficult to preview visually
• host ls -l produces a long list of all files.
• -rw-r--r-- 1 pam 880 Sep 28 1988 Aug.notes
• drwxr-xr-x 2 pam 512 Oct 23 1985 bin
• -rw-r--r-- 1 pam 129 Aug 20 1986 complex.f
• -rw------- 1 pam 129 Jul 2 1987 mbox
• -rw-r--r-- 1 pam 429 Aug 16 1418 outdis
• drwxr-xr-x 2 pam 512 Jan 22 1107 remodel
• -rwxr-xr-x 1 pam 102 Jun 19 1255 test.out

16
Using Filters with Pipes - grep

• To search a file for a specified string
• host ls -l grep Aug
• -rw-r--r-- 1 pam 129 Aug 20 1986 complex.f
• -rw-r--r-- 1 pam 4291 Aug 16 1418 outdis
• -rw-r--r-- 1 pam 880 Sep 28 1988 Aug.notes
• To search a file for all but specified string
• host ls -l grep -v Aug
• drwxr-xr-x 2 pam 512 Oct 23 1985 bin
• -rw------- 1 pam 129 Jul 21 1987 mbox
• drwxr-xr-x 2 pam 512 Jan 22 1107 remodel
• -rwxr-xr-x 1 pam 102 Jun 19 255 test.out

17
Using Filters - pipes, grep sort

• Consider the next example
• host ls -l grep Aug sort 4
• -rw-r--r-- 1 pam 129 Aug 20 1986 complex.f
• drwxr-xr-x 2 pam 512 Aug 23 1985 bin
• -rw-r--r-- 1 pam 880 Sep 28 1988 Aug.notes
• -rw-r--r-- 1 pam 929 Aug 16 1418 outdis
• -rwxr-xr-x 1 pam 972 Aug 19 1255 test.out

18
Constructing Simple Aliases

• Examine the following aliases
• alias rm rm -i
• Full pathnames are preferred
• alias cp /bin/cp -I
• Enclose complex commands in quotes
• alias ls "pwd /bin/ls -sFC"

Command
Alias name
Command line
19
More Complex Aliases

• Importing an argument
• alias chklog 'grep \! log. more'
• host chklog reg1
• alias cnt 'grep -c \! log.'
• alias f 'finger \!_at_lanl.gov'

Argument
List of files
Alias name
20
End of Module
Complete Using C Shell Function Exercises