Unix Tutorial

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Example: var=`command` Example: Following would execute date command and produced result would be stored in DATA variable. DATE=`date` echo "Current Date: $DATE" This would produce following result: Current Date: Thu Jul 2 05:28:45 MST 2009 TUTORIALS POINT Simply Easy Learning
CHAPTER 21 <strong>Unix</strong> – IO Redirections Most <strong>Unix</strong> system commands take input from your terminal and send the resulting output back to your terminal. A command normally reads its input from a place called standard input, which happens to be your terminal by default. Similarly, a command normally writes its output to standard output, which is also your terminal by default. Output Redirection: The output from a command normally intended for standard output can be easily diverted to a file instead. This capability is known as output redirection: If the notation > file is appended to any command that normally writes its output to standard output, the output of that command will be written to file instead of your terminal: Check following who command which would redirect complete output of the command in users file. $ who > users Notice that no output appears at the terminal. This is because the output has been redirected from the default standard output device (the terminal) into the specified file. If you would check users file then it would have complete content: $ cat users oko tty01 Sep 12 07:30 ai tty15 Sep 12 13:32 ruth tty21 Sep 12 10:10 pat tty24 Sep 12 13:07 steve tty25 Sep 12 13:03 $ If a command has its output redirected to a file and the file already contains some data, that data will be lost. Consider this example: $ echo line 1 > users $ cat users line 1 $ You can use >> operator to append the output in an existing file as follows: TUTORIALS POINT Simply Easy Learning
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Unix Tutorial
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ABOUT THE TUTORIAL Unix Tutorial UN
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Renaming Directories: .............
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Extended Shell Scripts: ...........
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Example: ..........................
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Trapping Signals: .................
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The main concept that unites all ve
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New UNIX password:******* Retype ne
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CHAPTER 2 Unix File Management All
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Displays all the files whose name s
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4. Fourth Column: represents file n
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CHAPTER 3 Unix Directories Adirecto
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Creates the directories docs and pu
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CHAPTER 4 Unix File Permission Setu
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$ls -l testfile -rw-rwxrwx 1 amrood
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The SUID and SGID bits will appear
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Note - The shell initialization pro
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The default secondary prompt is > (
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CHAPTER 6 Java Basic Utilities So f
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laserp-574 grace 82744 Nov 7 11:28
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CHAPTER 7 Unix Pipes and Filters Yo
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This pipe sorts all files in your d
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The process runs in the foreground,
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$kill -9 6738 Terminated Parent and
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CHAPTER 9 Unix Communication When y
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prompt on Turns prompt on. Dir List
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No Plan. Check all the logged in us
Page 55 and 56: ~ ~ ~ ~ ~ ~ ~ ~ "testfile" [New Fil
Page 57 and 58: Command CTRL+d CTRL+d CTRL+f CTRL+u
Page 59 and 60: ^G U U J Press CNTRL and G keys at
Page 61 and 62: IMPORTANT: Here are the key points
Page 63 and 64: POSIX shell ( sh) The different C-t
Page 65 and 66: CHAPTER 12 Unix- Using Variables Av
Page 67 and 68: NAME="Zara Ali" unset NAME echo $NA
Page 69 and 70: Command-Line Arguments: The command
Page 71 and 72: CHAPTER 14 Unix - Using Arrays Ashe
Page 73 and 74: CHAPTER 15 Unix - Basic Operators T
Page 75 and 76: val=`expr $b / $a` echo "b / a : $v
Page 77 and 78: else echo "$a -ge $b: a is not grea
Page 79 and 80: != Checks if the value of two opera
Page 81 and 82: ] is true. -x file Check if file is
Page 83 and 84: Right shift == String comparison fo
Page 85 and 86: -r file Checks if file is readable
Page 87 and 88: Example: #!/bin/sh a=10 b=20 if [ $
Page 89 and 90: There is only one form of case...es
Page 91 and 92: CHAPTER 17 Unix - Shell Loops Loops
Page 93 and 94: done This will produce following re
Page 95 and 96: 4) juice 5) appe 6) all 7) none #?
Page 97 and 98: CHAPTER 18 Unix - Loop Control So f
Page 99 and 100: 1 0 1 5 The continue statement: The
Page 101 and 102: \n new line \r carriage return \t h
Page 103 and 104: CHAPTER 20 Unix - Quoting Mechanism
Page 105: The Double Quotes: Try to execute t
Page 109 and 110: EOF 3 $ This is a simple lookup pro
Page 111 and 112: CHAPTER 22 Unix - Shell Functions F
Page 113 and 114: echo "Return value is $ret" This wo
Page 115 and 116: CHAPTER 23 Unix - Manpage Help All
Page 117 and 118: CHAPTER 24 Unix - Regular Expressio
Page 119 and 120: Try out the following address range
Page 121 and 122: sys:x:3:3:sys:/dev:/bin/sh sync:x:4
Page 123 and 124: [0-9] Matches a single number [a-zA
Page 125 and 126: (555)555-1213 (555)555-1214 (666)55
Page 127 and 128: dev /etc /lib /boot /home /mnt /pro
Page 129 and 130: $du -h /etc 5k /etc/cron.d 63k /etc
Page 131 and 132: CHAPTER 26 Unix - User Administrati
Page 133 and 134: $ groupdel developer This removes o
Page 135 and 136: CHAPTER 27 Unix - System Performanc
Page 137 and 138: CHAPTER 28 Unix - System Logging Un
Page 139 and 140: The combination of facilities and l
Page 141 and 142: Unix - Signals and Traps CHAPTER 29
Page 143 and 144: Trapping these signals is quite eas
Page 145 and 146: CHAPTER 30 Unix - Useful Commands T
Page 147 and 148: Ispell Emacs ex, edit Emacs Emacs C
Page 149 and 150: Command Dbx Gdb Make Nm Size Strip
Page 151 and 152: Reset Reset terminal mode Script Ke
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