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CSCI 330

THEUNIX SYSTEM

File operations

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OPERATIONS ON REGULAR FILES

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Create EditDisplay

ContentsPrint Others

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CREATING NEW FILES

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Create Regular

Files

vim,

emacs

nano,

etc.cat

Redirect

Command

Output

See Text Editors

Section

See shell

Section

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CREATING A FILE WITH CAT

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Example:

% cat > myfile

This is line 1 of input

Line 2 of input^d

%

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DISPLAY CONTENTS OF TEXT FILES

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Display Text

File contents

cat more less pg head tail

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VIEWING CONTENTS OF TEXT FILES

command cat can be used to

display/concatenate one or more files,

displaying the output all at once

Example: Display the contents of file assign1.txt

% cat assign1.txt

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more, less or "pg"

display the contents of one or more files

one page at a time

Space barto advance to next page bto go back a page

Enter Keyto advance to next line

Example: Display the contents of file assign1.txtone page at a time

% less assign1.txt 7

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head

displays the beginning portion of indicated file(s);

the default head size is 10 lines.

Example: Display first 20 lines of file assign1.txt

% head -20 assign1.txt

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tail

displays the ending portion of indicated file(s);

the default tail size is 10 lines.

Example: Display last 10 lines of file assign1.txt

% tail assign1.txt

% tail -10 assign1.txt

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PRINTING FILES

lpr

send a file to the default printer

printers available:csl or lpcsl (default)

frl or lpfrl

ucl or lpucl

Example:

% lpr -P frl assign1.txt

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PRETTY-PRINTING FILES

enscript

converts text file to PostScript, rtf or html

default: PostScript

sends output to printer

Example:

% enscript assign1.txt

Options:

-P to specify printer

-w to select output language

-o to specify output file11

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CHECKING PRINTING STATUS

Syntax: lpq [options]

Commonly used options:

-P printer shows print jobs on specific printer-U user-id shows print jobs for specific user

-l long format of listing

-a shows print jobs on all printers

Also: lprm to remove unwanted print job

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OPERATIONS ON TEXT & OTHER FILES

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Other File

Operations

Combine

contents

Extract

contents

Compare

files

Count

words

Compress

contentsSort

Uniquelines Encrypt/decrypt

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COMBINING CONTENTS OF FILES

Method 1: To vertically concatenate the contents of

two or more files, use catwith output redirection (>)

Syntax: cat file-1 file-2 file-3 > all-file

all-file will contain the combined contents of file-1,

file-2, and file-3 in top-down (vertical) fashion

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COMBINING CONTENTS OF FILES

Method 2: To horizontally concatenate contents

(columns/fields) of two or more files, usepaste

Syntax: paste file-1 file-2 > all-file

all-file will contain the combined contents of file-1

and file-2 in side-by-side (horizontal) fashion

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EXTRACTING CONTENTS OF FILES

To extract one or more fields from a file, use cut

fields are delimited by special character

default: TAB, change viad option common: :

must specify list of fields to be extracted

option -f

Example:

% cut -d: -f 5 /etc/passwd

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COMPARING FILES: COMM

The command named comm can be used to

compare lines that are common in two sortedfiles

Syntax: comm [options] file-1 file-2

The output contains three columns:

Column1 contains lines unique to file-1

Column 2 contains lines unique to file-2 Column 3 contains lines common to both files

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COMPARING FILES: DIFF

The command diffcompares two files line by line

Syntax: diff [options] file-1 file-2

If file-1 and file-2 are the same, no output is

produced

If file-1 and file-2 are not the same, diff reports a

series of commands that can be used to convert thefirst file to the second file

(via the patch command)

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DETERMINING FILE SIZE

Recall: The ls command with the option -l gives

the file size in bytes

Use wc to display the size of files as number of

lines, words, and characters

Syntax: wc file-list


-l display the number of lines-w display the number of words

-c display the number of characters

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FILE COMPRESSION

utilities to compress and uncompress files

common on Linux:

gzip, gunzip

file extension: .gz

Example:

% gzip assign1.txt

% gunzip assign1.txt.gz

Gzip and gunzip delete their inputs

So make a copy if you want one

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COMPRESS FILE CONTENTS

Bzip2

New, better compression

Old

compress/uncompress (.Z)

Windows-compatible

zip/unzip (.zip)

Do not delete their input!

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SORTING FILES

To sort a text file in ascending or descending order,

use sort

Syntax: sort [options] file-name


-r sort in reverse order

-n numeric sort-t field delimiter

-k field1[,field2]

-f ignore case 22

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REMOVING REPEATED LINES

uniq

removes repeated lines from a sorted input file,

sending unique (unrepeated) lines to standard

output

Syntax: uniq sorted-file-name


-c place a count of repeated lines at beginning of eachoutput line

-d display the repeated lines

-u display the lines that are not repeated23

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USERS DISK QUOTA

quota is upper limit of

amount disk space

number of files

for each user account

The command: quota -v

displays the users disk usage and limits

2 kinds of limits:

Soft limit: ex. 10MBMay be exceeded for one week

System will remind you when you log on Hard limit: ex. 12MB

Cannot be exceeded

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Documents

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