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Introduction to UNIX

Introduction to UNIX. F. Using C Shell Features. 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 )

william-garza
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Introduction to UNIX

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  1. Introduction to UNIX F. Using C Shell Features Using The C-Shell

  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 (>, <) 6. Append results of a command to existing files (>>, >>&) 7. Use Pipes to link command data (|) 8. Construct simple aliases (alias) 9. Recognize three basic error messages Using The C-Shell

  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. Using The C-Shell

  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). Using The C-Shell

  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 history=15 (.cshrc) • To display the last n commands. host% history 1 ls -l 2 cd ~ths 3 history Using The C-Shell

  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% ^lar^lear^ cd unix/class/handouts/learn Using The C-Shell

  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 Using The C-Shell

  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 Using The C-Shell

  9. Command Line Editing • Substitution changes any previous command: host% !7:s/0/1 cat /home/ths/sunclass1/basics/history/congrats • History list should be similar to the following: 7 cat /home/ths/sunclass0/basics/history/congrats 8 cat /home/ths/sunclass1/basics/history/congrats 9 history 10 cat /home/ths/sunclass1/basics/history/congrats 11 history Using The C-Shell

  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 > symbol to redirect STDOUT • Less-than < symbol to redirect STDIN • Ampersand & symbol to redirect STDERR Using The C-Shell

  11. Redirecting Input/Output • Examples: • host% cat filea > fileb (redirect creates fileb) • host% cat filec >> fileb (appends to fileb) • host% cat filed >& e.file (error msgs to e.file) • host% cat filex >>& e.file (append error to e.file) • host% mail -s “sub” address < file (get input from file) Using The C-Shell

  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. Using The C-Shell

  13. Using Pipes (Con’t) • But you must count each line on the screen: ted% ps -ax PID TT STAT TIME COMMAND 0 ? D 2:16 swapper 1 ? IW 0:00 /sbin/init - 2 ? D 0:12 pagedaemon 55 ? IW 2:59 portmap 60 ? IW 0:00 ypbind 62 ? IW 0:00 keyserv 73 ? S 1:57 (biod) 74 ? S 1:57 (biod) 75 ? S 1:57 (biod) 76 ? S 1:56 (biod) 87 ? IW 0:03 syslogd 95 ? IW 0:00 rpc.statd 97 ? IW 0:00 rpc.lockd 101 ? IW 11:01 automount 104 ? S 0:41 screenblank 109 ? S 20:21 update 112 ? IW 0:03 cron Using The C-Shell

  14. Use of Pipes - | (Con’t) • There are several solutions to this problem: • Solution 1 host% ps -ax > 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? Using The C-Shell

  15. Using Filters with Pipes • Lists are often difficult to preview visually: host% ls -lproduces 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 14:18 outdis drwxr-xr-x 2 pam 512 Jan 22 11:07 remodel -rwxr-xr-x 1 pam 102 Jun 19 12:55 test.out Using The C-Shell

  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 14:18 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 11:07 remodel -rwxr-xr-x 1 pam 102 Jun 19 2:55 test.out Using The C-Shell

  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 14:18 outdis -rwxr-xr-x 1 pam 972 Aug 19 12:55 test.out Using The C-Shell

  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 Using The C-Shell

  19. More Complex Aliases • Importing an argument: alias chklog 'grep \!*log.* | more' • host% chklog reg1 • alias cnt 'grep -c \!* log.*' • alias f 'finger “\!*”@lanl.gov' Argument List of files Alias name Using The C-Shell

  20. End of Module Complete Using C Shell Function Exercises Using The C-Shell

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