Transcript Text Editors - Northern Illinois University

CSCI 330
THE UNIX SYSTEM
File operations
OPERATIONS ON REGULAR FILES
CSCI 330 - The UNIX System
Create
Edit
Display
Contents
Print
Others
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CREATING NEW FILES
cat
vim,
emacs
nano,
etc.
See Text Editors
Section
CSCI 330 - The UNIX System
Create Regular
Files
Redirect
Command
Output
See shell
Section
3
CREATING A FILE WITH CAT
CSCI 330 - The UNIX System
Example:
% cat > myfile
This is line 1 of input
Line 2 of input
^d
%
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DISPLAY CONTENTS OF TEXT FILES
cat
more
less
pg
head
CSCI 330 - The UNIX System
Display Text
File contents
tail
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VIEWING CONTENTS OF TEXT FILES

CSCI 330 - The UNIX System
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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VIEWING CONTENTS OF TEXT FILES

CSCI 330 - The UNIX System
“more”, “less” or "pg"
display the contents of one or more files
one page at a time
Space bar – to advance to next page
 b – to go back a page
 Enter Key – to advance to next line

Example: Display the contents of file “assign1.txt”
one page at a time
% less assign1.txt
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VIEWING CONTENTS OF TEXT FILES

CSCI 330 - The UNIX System
“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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VIEWING CONTENTS OF TEXT FILES

CSCI 330 - The UNIX System
“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

printers available:
csl or
frl or
ucl or
lpcsl
lpfrl
lpucl
(default)
CSCI 330 - The UNIX System

“lpr”
send a file to the default printer
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


CSCI 330 - The UNIX System

Options:
-P
to specify printer
-w
to select output language
-o
to specify output file
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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
CSCI 330 - The UNIX System

Also: “lprm” to remove unwanted print job
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OPERATIONS ON TEXT & OTHER
FILES
Other File
Operations
Extract
contents
Compare
files
Count
words
Compress
contents
Sort
Unique
lines
Encrypt/
decrypt
CSCI 330 - The UNIX System
Combine
contents
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COMBINING CONTENTS OF FILES

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
CSCI 330 - The UNIX System
Method 1: To vertically concatenate the contents
of two or more files, use cat with output
redirection (>)
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COMBINING CONTENTS OF FILES

Method 2: To horizontally concatenate contents
(columns/fields) of two or more files, use paste

“all-file” will contain the combined contents of
file-1 and file-2 in side-by-side (horizontal)
fashion
CSCI 330 - The UNIX System
Syntax: paste file-1 file-2 > all-file
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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 via –d option
 common: “:”


must specify list of fields to be extracted

option -f
CSCI 330 - The UNIX System

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 sorted files

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
CSCI 330 - The UNIX System
Syntax: comm [options] file-1 file-2

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COMPARING FILES: DIFF

The command diff compares two files line by line
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
the first file to the second file
(via the “patch” command)

CSCI 330 - The UNIX System
Syntax: diff [options] file-1 file-2
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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

CSCI 330 - The UNIX System
Syntax: wc file-list
 Commonly used options:
-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:


.gz
Example:
% gzip assign1.txt
% gunzip assign1.txt.gz

CSCI 330 - The UNIX System
gzip, gunzip
 file extension:

Gzip and gunzip delete their inputs

So make a copy if you want one
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COMPRESS FILE CONTENTS

Bzip2

Old


compress/uncompress (.Z)
Windows-compatible
CSCI 330 - The UNIX System

New, better compression
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

Commonly used options:
-r
-n
-t
-k
-f
sort in reverse order
numeric sort
field delimiter
field1[,field2]
ignore case
CSCI 330 - The UNIX System
Syntax: sort [options] file-name
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REMOVING REPEATED LINES

Syntax: uniq sorted-file-name
 Commonly used options:
-c place a count of repeated lines at beginning of each
output line
-d display the repeated lines
-u display the lines that are not repeated
CSCI 330 - The UNIX System
“uniq”
removes repeated lines from a sorted input file,
sending unique (unrepeated) lines to standard
output
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USER’S DISK QUOTA

quota is upper limit of

for each user account

The command: quota -v


displays the user’s disk usage and limits
2 kinds of limits:

CSCI 330 - The UNIX System

amount disk space
number of files
Soft limit: ex. 10MB
May be exceeded for one week
 System will remind you when you log on


Hard limit: ex. 12MB

Cannot be exceeded
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