text processing in os

8/7/2019 Text Processing in OS

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Text Processing :-Cut :-

To extract data from each line of a text file

can be used for a file that contains data records so that each line consist of one or

more fields separated by tab characters.

Flag :-

-c characterlist specify a list of characters to be cut from each

line

-f fieldlist Specify a list of fields to be cut from each line.

-d character To override the character to be interpreted

as the field delemiton.

-s To suppress lines that do not hr the specified

delimiter character.

Ex :-

1 If you want to extract the first field,cut f1 file1

2 if you want to cut the chars 2 to 6 ,cut c2 -5 file1

3 if you want to cut all chars in the first field up to the first 5 character, use thefollowing command.

4 Cut ds s f1 file1

ex : invokes the ex editor to edit one or more files

fmt : can be used to format files to a 72 characters line by default.

- preserves the blank lines in the i/p file as well as the spacing between words.- U can modify the line length using the width flag

Fold : can be used to generate multiple lines from a single line by splitting the line at the

specified position


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- By def, the line length is 80 bytes.

Flag :

-b specify the position in bytes.

-s split a line after the last space at a position that is less than or equal to the

specified width

-w width specify the line width.

Ex : if you want to split the line at byte position 40

fold -w 40 file1 > file2;

if you do not want to split words,

fold w 40 s file1>file2.

Join :- can be used to merge 2 files (one can be std. Input to execute a third file (Which can be

std. O/p)

- each line in the file is merged on the basis of a field that has the same value in bothi/p files to create one line in the o/p file.

- The filed in each file are separated by either a space or the tab character.

Flag :-- -1 field or j1 field specify that the join should be made on the basis of

field in the first file.

- -2 field or j2 field specify that the join should be made on the basisof the field in the second file.

- -e string specify that blank fields in the o/p file bereplaced by the specified string.

- -o field.fieldnumber specify that the o/p should consist of the specifiedfields.

u can specify multiple fields by separating them

with commands

- -t char Modify the field seperator char from the default

value of the space.


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Ex :-

1 If u want to join the 2 files & display the matching lines as well as theNon-matching lines from the specified file.

- Join a1 file1 file2

paste :-

can be used to paste lines from one or more files(one of them can be std. Input)

to the std. O/p, which can be redirected to a file.

- This comm. concatenates the line from each input file to the output file, separating

them by default with the tab character.

Flag :-

-d list specify chars, that will be used to separate corresponding lines from

the i/p files in the o/p files.

u can specify multiple chars if u have multiple i/p files.-s merge subsequent lines from the i/p file for each i/p file, one at a time,

separated by the specified delimiter char.

Ex :-

- if u want to modify def. Separate filename tab to / =>past -d / file1 file2

Sort :-

Is used to sort one or more files in the specified order by the specified key.


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It can also be used to merge files that hr already been sorted.

Flag :-

- -k key specify the key on which to sort the specification for the key

inchides the starting field & column position & the end field

& col. Position.

- -A Specify the sorting be done according to ASCII sequence.

- -c check whether the specified files are sorted according to the

specified key & order.

- -d sort according to dictionary order.

- -f change all letters to uppercase before the sort.

- -i Ignore nondisplayable characters. For comparison.

- -m merge presorted of files.

- -n sort according to numerical valued.

- -o file redirect the o/p to the specified file instead of to the std. O/p

- -r sort the o/p in the reverse order of the specified order.

- -u create only one line in the o/p for lines that sort identically.

Ex :-

1 if you want to sort in the reverse order,sort r file1

2 if you want to sort according to alphabetic ordersort d file1

tr :-

to translate or delete characters from std. I/p to generate std. O/p./

- translate specified chars in the i/p from the input to generate the output.- Delete specified chars in the i/p from the input to generate the output.- Delete all but the first occurrences of the specified chars.


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Flag :-

-c translate all but the specified chars using the specified new

characters.

-d delete the specified chars.

-s delete all but the first occurrence of the specified chars.

Specify i/p & o/p sequence of chars

[char1-char2] to specify a range of chars. Including char1 & char2

[char1*number] to specify number occurrences of char.

[char *] to specify the use of as many occurrences as are needed

of character so that the i/p string of chars. To be

translated matches the o/p chars.

[:charlist:] to specify a list of chars. As the i/p or o/p string.

The charlist can be upper, lower, alph, space, digits,

& so on.

Ex :-

1 if u want to change the double quotes to spaces,tr \ < file1

2 if u want to change all lowercase letters to uppercase lettertr [:lower:] [:upper:]


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Can be used to eliminate duplicate adjacent lines from a file or from std. I/p to

Generate std o/p or another file.

- Also it is possible to compare only part of a line for comparison by usingCertain flags.

Flag :-

-c precede each line with a number while displaying the o/p (the no.

specifies the no of recursences of the line in the i/p file).

-d display only th elines that occur multiple times adjacent to each other in

the i/p file.

-u display only the lines that appears only once in the i/p file.

-s no. of characters

or

+noofchars specify the no of chars from the start of a line that will be ignored

while comparing adjacent lines.

-no of fields

or

+no of fields specify the no of fields from the start of a line that will be ignored

while comparing adjacent lines

Ex :-

1 if u want to find unique lines in file12 if u want to display only the duplicate line

uniq d file1

3 if u want to display the lines that appear only once in file1uniq u file1

Sed :-

To edit a file using a script


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- in the script, u can specify commands to edit one or more lines according rulesspecified as part of one or more commands.

Flag :-

-e command use the specified sed comm.. to edit the file.

-f filename use the filename as the editing script to edit the file.

-n suppress messages from sed.

Ex :-

1 if u want to print the line no of the line in which a specified pattern is found,sed e /sed/= file1

text processing in os

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