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Shell Scripting

Shell Scripting. hmehta.scs@dauniv.ac.in. Applications of Shell Scripts. Task 1: There is a text file having data in columns. Store a particular column in a different file. Task 2: Sort a file. Task 3: Apply sorting in the output file of Task 1.

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Shell Scripting

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  1. Shell Scripting hmehta.scs@dauniv.ac.in

  2. Applications of Shell Scripts Task 1: There is a text file having data in columns. Store a particular column in a different file. Task 2: Sort a file. Task 3: Apply sorting in the output file of Task 1. Task 4: Store only unique data in the output file.

  3. Applications of Shell Scripts Task 5: Store the data which satisfy the given condition. Task 6: Transfer the file to the client’s machine for the further processing. Task 7: Determine whether the executed program completed successfully or not. Task 8: In case of failure produce the signal for error.

  4. Solution #!/bin/ksh HOST=‘ftp.myserverid.mydomain’ USER=‘MyUserid’ PASSWD=‘MyPassword‘ FILE=“filename” OUTFILE=“newfile” MAILINGLIST=“supportmail.lst” LOG=“logfile” cut –c5,6 $FILE| sort| uniq > $OUTFILE awk '{if ($2 > 30) print $1}‘ $OUTFILE

  5. Solution ftp -n $HOST > /tmp/ftp.worked 2> /tmp/ftp.failed <<END_SCRIPT user $USER pass $PASSWD put $FILE quit END_SCRIPT EXITSTATUS=$? if [ $EXITSTATUS != "0" ] then for PEOPLE in `cat $MAILINGLIST` do /usr/bin/mailx –s “a process is failed” $PEOPLE [$? –ne 0] && echo “$PEOPLE mailx failed” >>$LOG done fi

  6. Applications of Shell Scripts Requirement: Need to execute a program on a particular time (System time). ?

  7. Applications of Shell Scripts Requirement: Logging the information about the execution of a job. ?

  8. Applications of Shell Scripts Requirement: Need to execute a program on a particular time (System time) but after successful completion of a job. ?

  9. Applications of Shell Scripts Requirement: Need to execute a program on a particular time (System time) but after successful completion of a job. Also check for the existence of a particular file. ?

  10. Applications of Shell Scripts Requirement: Need to know that whether a particular job completed successfully or not. ?

  11. Applications of Shell Scripts Requirement: Sending Mail/ SMS in case of error in the execution. ?

  12. Applications of Shell Scripts Requirement: Working like database on the text files. ?

  13. Applications of Shell Scripts Requirement: Fetching columns/ rows from a file, counting the records, filtering the data,sorting the data, Pattern matching/ replacing. ?

  14. Applications of Shell Scripts Requirement: Handling CSV Files. ?

  15. Applications of Shell Scripts Requirement: Periodic Monitoring the system activities like disk space utilization etc. ?

  16. Applications of Shell Scripts Requirement: Sending / Receiving data to / from Remote location/computer. ?

  17. Applications of Shell Scripts Requirement: Checking for the existence and permission for a file. ?

  18. Applications of Shell Scripts Requirement: System administrators, for automating many aspects of computer maintenance, user account creation etc. ?

  19. Applications of Shell Scripts Requirement: Application package installation tools. ?

  20. Applications of Shell Scripts Requirement: Application startup scripts, especially unattended applications. ?

  21. Applications of Shell Scripts Requirement: Data Synchronization. ?

  22. Applications of Shell Scripts Requirement: Interface between Os and other tools/language like Java, Oracle, FTP. ?

  23. Applications of Shell Scripts Requirement: Log Rotation. ?

  24. Applications of Shell Scripts Requirement: Purging of old files and data. ?

  25. Applications of Shell Scripts Requirement: Removing blank files and File comparison. ?

  26. The Shell & Shell Script • A shell is a command interpreter turns the input text in to actions. • Bourne Shell • Bourne Again Shell • Korn Shell • C Shell • etc. .. .. .. • A Shell Script is a logical sequence of commands.

  27. The Anatomy of a Command • grep –i localhost /etc/hosts Command Option Arguments Options Change the behavior of a command Arguments control what the command act upon

  28. Running the Shell Script • Type the name of a program and some command line options. • The shell reads this line, finds the program and runs it, feeding it the specified options. • The shell establishes 3 I/O channels: • Standard Input • Standard Output • Standard Error

  29. The Shebang (#!) • The Shebang is a special comment. • It specifies which shell to use to execute this shell script. • If no “#!” found, the current shell will be used to run the script. • Example #!/bin/ksh

  30. Two ways to execute the Shell • Set the permission attributes as a executable file then execute it like a command. OR • Invoke the shell explicitly. sh backup8pm.sh

  31. Debugging the Shell Script • Running a script in debug mode will print each line of shell script before it executes. • Enable debug mode after adding the –v after shell interpreter’s name in Shebang.

  32. Advantages • Writing a shell script is much quicker than writing the equivalent code in other programming or scripting languages. • Shell scripts have no compilation step, so the script can be executed quickly while debugging.

  33. Disadvantages • One significant disadvantage of using shell scripts is that they can run slowly due to the need to create potentially many new sub-processes for each of the many commands executed. • Simple sh scripts can be quite compatible with the extremely diverse range of Unix but more complex shell scripts can fail because of the many subtle differences between shells.

  34. Programs and Standard I/O Program Standard Input (STDIN) Standard Output (STDOUT) Standard Error (STDERR)

  35. Overwritingthe Standard I/O Device • Input/ Output Redirection

  36. Pipes • A pipe is a holder for a stream of data. • A pipe can be used to hold the output of one program and feed it to the input of another. prog1 prog2 STDOUT STDIN

  37. Regular Expression • Regular Expressions provide a concise and flexible means for identifying text of interest. • Examples: • [abc] matches a single a b or c • [a-z] matches any of abcdef…xyz

  38. Regular Expression • Examples: • .at matches any three-character string ending with "at", including "hat", "cat", and "bat". • [hc]at matches "hat" and "cat". • [^b]at matches all strings matched by .at except "bat". • ^[hc]at matches "hat" and "cat", but only at the beginning of the string or line. • [hc]at$ matches "hat" and "cat", but only at the end of the string or line.

  39. Regular Expression • Examples: • .at matches any three-character string ending with "at", including "hat", "cat", and "bat". • [hc]at matches "hat" and "cat". • [^b]at matches all strings matched by .at except "bat". • ^[hc]at matches "hat" and "cat", but only at the beginning of the string or line. • [hc]at$ matches "hat" and "cat", but only at the end of the string or line.

  40. Regular Expression Used by • grep “Get Regular Expression and Print” – search files line by line • sed Simple Editing tool, right from the command line • awk Scripting language, executes “program” on matching lines

  41. Important Commands (UNIX) • touch: create a new file / update timestamp of existing file. • grep: search for a specified string or pattern • chmod/ chown/ chgrp: Change permissions / ownership / group on a file • du/ df: Display hard disk information. • find:find a file • sort: sort a file into alphanumeric order (by lines.) • sed: Invoke the stream editor. • tr: Translate characters. • awk: Invoke the awk scripting language. • split: Split up a file into smaller chunks.

  42. Important Commands (UNIX) • at: Run a command / script at a specified time and date. • Cut: cut specified field(s)/ character(s) from lines in file(s) • more, less, and pg: page through a file • head/ tail: display the start/ end of a file • cmp: compare two files and list where differences occur (T/B) • diff : compare the two files and display the differences (T) • wc: display word (or character or line) count for file(s) • mail/ mailx/ Mail: simple email utility available on Unix systems. • paste: The paste command allows two files to be combined side-by-side.

  43. Important Commands (WinNT) • AT: Schedule a command to run at a later time • ATTRIB: Change file attributes • CACLS: Change file permissions . • CleanMgr: Automated cleanup of Temp files, recycle bin • COMP: Compare the contents of two files or sets of files • FC: Compare two files • FDISK: Disk Format and partition • FIND: Search for a text string in a file • Magnify: Display windows magnification • MAPISEND: Send email from the command line • MEM: Display memory usage

  44. Important Commands (WinNT) • MORE: Display output, one screen at a time • MSG: Send a message • NET: Manage network resources • PERFMON: Performance Monitor • QGREP: Search file(s) for lines that match a given pattern. • SCHTASKS: Create or Edit Scheduled Tasks • SCLIST: Display NT Services • SORT: Sort input • TOUCH: Change file timestamps • USRSTAT List domain usernames and last login

  45. Book for UNIX

  46. Book for WinNT

  47. Any Questions Thank You 

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