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UNIX OS

UNIX OS. DAY – 1 Session – 2. Objectives. Identify the standard input, output and error files Use input, output & error redirection Use of Pipes & tee command Hard Link & Soft Link. Objectives (contd.). Text manipulation command head, tail, cut, paste, sort & tr

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UNIX OS

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  1. UNIX OS DAY – 1 Session – 2 MBT – NCS UNIX OS

  2. Objectives • Identify the standard input, output and error files • Use input, output & error redirection • Use of Pipes & tee command • Hard Link & Soft Link © CMC Limited A TATA Enterprise

  3. Objectives (contd.) • Text manipulation command head, tail, cut, paste, sort & tr • File Access Permission (FAP) command chmod, chown, chgrp • Locating a file using the find command • The vi editor to create & manage document files © CMC Limited A TATA Enterprise

  4. Standard Files • Standard Input File • The keyboard is referred to as the standard input file • In Unix, all open files, including the standard files, are assigned a number called the file descriptor. The file descriptor 0 (zero) is assigned to the standard input file © CMC Limited A TATA Enterprise

  5. Standard Files (contd.) • Standard Output File • The monitor is referred to as the standard output file • The file descriptor 1 is assigned to the standard output file © CMC Limited A TATA Enterprise

  6. Standard Files (contd.) • Standard Error File • The monitor is also the standard error file • The file descriptor 2 is assigned to the standard error file. © CMC Limited A TATA Enterprise

  7. Redirection Redirection changes the assignment for standard input, output & error • Input Redirection • The following examples illustrate the use of input redirection $ cat < test1 $ cat 0< test1 • Output Redirection • The following example illustrate the use of output redirection $ cat test1 > test2 $ cat test1 1> test2 $ cat test2 >> test1 ( >> is equal to append ) © CMC Limited A TATA Enterprise

  8. Redirection (contd.) • Error Redirection • The following example illustrate the use of error redirection $ cat datafile 2> error-mesg © CMC Limited A TATA Enterprise

  9. Pipe • Pipes are used to connect to streams • Syntax : command | command #The vertical bar ( | ) • It indicates to the shell that the output of the command before ‘|’ is to be send as an input to the command after it • The following example illustrate the use of pipe : • Without a pipe: $ ls – l > listoffiles $ less listoffiles • With a pipe: $ ls – l | less © CMC Limited A TATA Enterprise

  10. tee command • A tee command takes standard input, writes to standard output & to file(s). • Syntax: command | tee filename • The following example illustrate the use of tee command: Without a tee command: $ ls -l > listoffiles $ cat listoffiles • With a a tee command: $ ls –l | tee listoffiles © CMC Limited A TATA Enterprise

  11. Links • A link allows a file to have more than one name and yet maintain a single copy • Changes to one file will reflect in the other • Links are of two types : hard link & soft link (symbolic link) © CMC Limited A TATA Enterprise

  12. Hard Link • To create a hard link the command is ln filename1 filename2 • The inode number for filename1 & filename2 is same. © CMC Limited A TATA Enterprise

  13. Soft link (Symbolic link) • A soft link extends to different file systems. • A soft link links to a directory. • Soft links takes a different inode number then the actual file. • To create a hard link the command is ln -s filename1 filename2 © CMC Limited A TATA Enterprise

  14. Text manipulation commands • head command – allows the user to see the first few lines of the file. Syntax : head option filename • tail command – allows the user to see the last few lines of the file. Syntax : tail option filename • cut command – allows the user to slice the file vertically. Syntax : cut option filename • paste command – allows the user to concatenate the file vertically. Syntax : paste option filename © CMC Limited A TATA Enterprise

  15. Sort command • Sorts the data of the file. • It allows checking of field orders • It sorts the data on ASCII code sequences • Syntax: sort option –o output file data file © CMC Limited A TATA Enterprise

  16. Sort options © CMC Limited A TATA Enterprise

  17. Sorting (contd.) • Sorting on secondary key eg: sort –t “|” +2 –3 +1 filename -- This will sort the file on primary field 2 and secondary field 1. The –3 means where to stop sorting. • Sorting on columns in the fields eg: sort –t “|” +4.6 –4.8 filename -- This will sort the on the 2 characters from 6 to 8 in the fourth field. © CMC Limited A TATA Enterprise

  18. tr command • It is a filter that manipulates individual characters in a file. • Syntax : tr option expression1 expression2 standard input • The input is from standard input and not from the file. • Eg: tr ‘|/’ ‘,-’ < filename --- replace all | & \ with , & - tr ‘[a-z] ‘ ‘[A-Z]’ < filename --- replace all a-z with A-Z © CMC Limited A TATA Enterprise

  19. tr options • -d ‘’ - delete character Eg: tr –d ’|’ < filename • -s ‘’ – squeeze Eg: tr –s ‘ ‘ < filename d © CMC Limited A TATA Enterprise

  20. File Acces Permission (FAP) • File Access Permission (FAP) refer to the permissions associated with a file with respect to the following: • The mode of the file • The file owner • The group owner • The other users © CMC Limited A TATA Enterprise

  21. Assigning Permission to the File • The chmod command • Syntax : chmod mode file/directory • The chmod command is used to change the permissions associated with a file/directory © CMC Limited A TATA Enterprise

  22. Absolute modes with chmod © CMC Limited A TATA Enterprise

  23. Relative modes with chmod © CMC Limited A TATA Enterprise

  24. chown command • chown command is used to change the owner of the file. This command is irreversible. • Syntax: chown owner filename/directory © CMC Limited A TATA Enterprise

  25. chgrp command • chgrp command is used to change the group of the file. This command is irreversible. • Syntax: chgrp owner filename/directory © CMC Limited A TATA Enterprise

  26. Locating a file • The find command • Syntax: find option path • The find command is used to locat a file in a particular directory and its sub-directories. It is th most commonly used command for locating files anh has various option for advanced searches © CMC Limited A TATA Enterprise

  27. Editors • A text editor is used to create & manage text files & document. An editor is an application software that is usually bundled with an OS • Functions of an Editor • Create a file • Open an existing file • Copy & Pate text • Search for text • Handle a large amount of data © CMC Limited A TATA Enterprise

  28. The vi editor • The vi editor is a visual editor used to create and edit a text file, documents & programs. In Unix vi is a symbolic link to the vim editor, which is an imporved version of vi editor. • Getting started with vi • The vi editor is invoked by the following command at the Unix prompt vi filename © CMC Limited A TATA Enterprise

  29. The vi Editor (contd.) • vi is the screen editor. • It works in three modes – command, text, escape. • In the command mode the cursor movements can be handled. • In text mode the insert, append, change, open of text operation are handled. • In ex mode text search, changing visual interface, saving & quitting is handled. © CMC Limited A TATA Enterprise

  30. Summary • You can redirect input, output & errors to a file other than the standard files by the file descriptors along with the redirection symbols < , > and >>, 2> • A pipe is a feature through which standard output of a command or user program can be sent as the standard input to another command or user program • A tee command takes standard input & writes to standard output & to file(s) © CMC Limited A TATA Enterprise

  31. Summary (contd.) • A link allows a file to have more than one name and yet maintain a single copy, there are 2 types of links hard & soft • Text manipulation commands head, tail allows horizontal slicing of file whereas cut and paste command allows vertical slicing of file(s) • sort command sorts the data of the file. © CMC Limited A TATA Enterprise

  32. Summary (contd.) • tr is a filter that manipulates individual characters in a file. • File Access Permission (FAP) command chmod, chown, chgrp are used to manipulate files & direcories • To locate a file find command is used. • The vi editor is used to create and edit documents © CMC Limited A TATA Enterprise

  33. Recall • Recall © CMC Limited A TATA Enterprise

  34. Assignments • Day 1 Session 2 Assignments © CMC Limited A TATA Enterprise

  35. END of DAY 1/SESSION - 2 MBT – NCS UNIX OS

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