hmehta.scs@dauniv;ac.in school of computer science and information technology devi ahilya...
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hmehta.scs@dauniv;ac.inSchool of Computer Science and Information Technology
Devi Ahilya Vishwavidyalaya
Shell Scripting
SCSITDAVV
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.
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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.
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Solution
#!/bin/kshHOST=‘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
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Solutionftp -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
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Applications of Shell Scripts
Requirement: Need to execute a program on a particular time (System time).
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Applications of Shell Scripts
Requirement: Logging the information about the execution of a job.
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Applications of Shell Scripts
Requirement: Need to execute a program on a particular time (System time) but after successful completion of a job.
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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.
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Applications of Shell Scripts
Requirement: Need to know that whether a particular job completed successfully or not.
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Applications of Shell Scripts
Requirement: Sending Mail/ SMS in case of error in the execution.
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Applications of Shell Scripts
Requirement: Working like database on the text files.
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Applications of Shell Scripts
Requirement: Fetching columns/ rows from a file, counting the records, filtering the data, sorting the data, Pattern matching/ replacing.
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Applications of Shell Scripts
Requirement: Periodic Monitoring the system activities like disk space utilization etc.
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Applications of Shell Scripts
Requirement: Sending / Receiving data to / from Remote location/computer.
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Applications of Shell Scripts
Requirement: Checking for the existence and permission for a file.
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Applications of Shell Scripts
Requirement: System administrators, for automating many aspects of computer maintenance, user account creation etc.
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Applications of Shell Scripts
Requirement: Application package installation tools.
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Applications of Shell Scripts
Requirement: Application startup scripts, especially unattended applications.
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Applications of Shell Scripts
Requirement: Interface between Os and other tools/language like Java, Oracle, FTP.
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Applications of Shell Scripts
Requirement: Purging of old files and data.
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Applications of Shell Scripts
Requirement: Removing blank files and File comparison.
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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.
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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
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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
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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
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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
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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.
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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.
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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.
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Programs and Standard I/O
ProgramProgramStandard Input
(STDIN)
Standard Output
(STDOUT)
Standard Error
(STDERR)
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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.
prog1prog1 prog2prog2STDOUT STDIN
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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
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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.
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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.
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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
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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.
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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.
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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
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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
hmehta.scs@dauniv;ac.inSchool of Computer Science and Information Technology
Devi Ahilya Vishwavidyalaya
Thank You
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