june 1, 1999manipulating files1 introduction to unix e. manipulating files

June 1, 1999 Manipulating Files 1

Introduction to UNIX

E. Manipulating Files


Basic File Manipulation

Performance Objectives1. View a selected file (cat, more)

2. View leading or trailing segments of a file (head, tail)

3. Copy and move files (cp, mv)

4. Use Wild Card Characters (*, ?, [])

5. Identify file permission attributes (rwx)

6. Set file permissions (chmod, umask)

7. Print Files (lpr, lpq, cancel, pr)

8. Record the Screen Image (script)9. Locate a file (find)


Basic File Manipulation

Performance Objectives- continued10. Archive files (tar)11. Check spelling (ispell, look)12. Search for specified string in a file (grep)13. Order a file by a specified column (sort)


Viewing a File - cat

• Three forms: Read each file in sequence and display it on

standard output. host% cat file1 file2

Combine files and place result in another. host % cat file1 file2 > file3

Make a file from standard input (until ^d) host% cat >file


Viewing a File - more

• View a file in a controlled manner. more [options] filename host% more passwd

• Note more --- xx% in the lower left corner.

• <RETURN> moves one line at a time.

• SPACEBAR moves one screen at a time.

• Use /keyword to advance to desired information.


Viewing the Head or Tail

• View the first 10 lines of a file:host% head passwd

• Use -20 to see 20 lineshost% head -20 passwd

• View the last 10 lines of a file:host% tail passwd

• Use -f to continuously monitor a filehost% tail -f /var/log/syslog


Wild Cards - *

• Wildcards permit selection criteria

• Note the following list:host% lsAprmbox Junmbox bin misc_memosAugmbox Marmbox calendar newjunkDecmbox Maymbox doc_memo newsrcFebmbox Novmbox junk outJanmbox Octmbox login test.fJulmbox Sepmbox mbox test.out


Wild Cards - * (Con’t)

• Use an asterisk * to list filenames containing certain patterns.

host% ls *junk

junk newjunk

host% ls *mb

No match


Wild Cards - * (Con’t)

• Carefully observe the placement of asterisks host% ls *mb*

Aprmbox Janmbox Maymbox mbox

Augmbox Julmbox Novmbox

Decmbox Junmbox Octmbox

Febmbox Marmbox Sepmbox


Wildcards - [ ]

• Use Brackets to define a range:host% ls doc/memo.[1-5]

doc/memo.1

doc/memo.3

doc/memo.5


Wildcards - ?

• Use the question mark to define a specific number of character positions:

host% ls test.???

test.out

• Note that this ls did not display the file test.f


File Commands - cp

• The copy command copies a file to a new location:

host% cp passwd docs/newfile

host% cp -i ~dhk/file2 docs/newfile

overwrite newfile?

host% cp ~dhk/passwd .


File Commands - mv

• Command syntax:host% mv oldfile newfile

host% mv -i ~dhk/file2 calendar

remove calendar?

host% mv calendar docs

• Note possible use of set noclobber in .cshrc.


File Commands - rm

• Command syntax:host% rm oldfile

host% rm -i newfile

rm: remove newfile?

host% rm -r *

• Removes ALL files and directories - BE CAREFUL


File Commands - rm

• To remove filenames with certain patterns:host% rm *junk

host% rm *mb*


Protecting Your Files

• Use the -l option to reveal the permissions:host% ls -ldrwxr-xr-x 2 ths 512 Oct 23 1985 bin

-rw-r--r-- 1 ths 129 Nov 20 1985 complex.f

-rw------- 1 ths 129 Jul 2 10:05 mbox

• File Permissions r = read w = write x = execute/search



• Who has permission? d rwx r-x r-x 2 ths 512 Oct 23 1985 bin - --- --- ---

u g o

user (owner)

group

other (world)



• chmod changes permissions after a file has been created.

• umask in your .cshrc sets the file creation mask for all files.


Protecting Your Files - umask• Command syntax:

host% umask value

• Octal values deny access privileges 1 x 4 r 7 rwx 2 w 5 rx 3 wx 6 rw

default value 22 Group and Others have no write permission. most restrictive 77 Group and Others have no permissions.


Migrating Privileges

• The cp command uses the umask privileges.

• The mv command transfers existing privileges for a file.


Protecting Your Files - chmod

• Command syntaxhost% chmod mode file ...

• The option "mode" defines all permissions or changes existing permissions



• chmod uses the following syntax: chmod ug+w filename

who op permission u = r

g + w

o - x

a



• Consider the following examples:-rw-r--r-- 1 ths 129 Nov 20 1985 memos

drwxr-xr-x 2 ths 512 Oct 23 1985 pri.dir

-rw------- 1 ths 129 Jul 2 10:05 mbox

• Give write permission to group and others.host% chmod go+w memos

• Remove read/search from group.host% chmod g-rx pri.dir

• Read permission for all.host% chmod a=r mbox


Printing Files

• Local print commands lpr, lp lpq, lpc status lprm, cancel pr

• Contact consult for output from mode


Capturing screen input-script

• To capture everything that shows up on the screen, use script

host.21% script errors

Script started, file is errors

host.1% CC program.c -o program.x

. . .

host.2% exit

Script done, file is errors

host.22%


Finding Files with find

• find will search a directory tree

• You need to have search privileges for treefind . -name a.out -print

• Searches can take a long time, background them

find / -name crack -print > crack.found &

• See man page for other options


Archiving files with tar

• Tape Archive (tar)

• Used to create one file from a directory tree

• Create a tar filetar cvf /tmp/newfile.tar .

• Expand a tar filetar xvf product.tar

• May have to uncompress it firstuncompress tex.tar.Z ; tar xvf tex.tar


Check spelling - spell and look

• Most Unix systems have both

• Not as good as word processors

• Dumps words that are not in its spelling listspell project.report

• Now how do you spell seperate?look sep


Use of Filters

• A filter takes its input from a file, performs some operation on that input, and writes the result to standard output.

• Common UNIX filters are grep more sort wc


Global Regular Expression Parser• grep - Global Regular Expression Parser

Searches a file for a specified string:host% grep ths passwdths:6q3y/n8TQp2WU:1059:8010:Ted Spitzmiller, 081347,8010x33d:/home/sunclass1/ths:/bin/csh

• wc - Word Count, shows the number of lines, words, and charactershost% wc project.report


Use of Filters - sort• Performs an alphanumeric sort of a file.

host% sort [options] [file(s)]

• Example of use:host% ls -l > x Routes the result to file "x" host% sort x Sorts on first field (blank delimiter)

0 -rw------- 1 ths 0 Jun 4 09:30 dead.letter 0 -rw-r--r-- 1 ths 0 Apr 30 14:34 x 1 -rwx------ 1 ths 31 Dec 17 1993 startAR* 1 -rwx-----x 1 ths 115 Nov 25 1991 cfs.size* 1 drwx------ 2 ths 512 Feb 29 1996 News/ 1 drwx--x--x 2 ths 512 Aug 15 1996 cfs.dir/ 1 drwxr-xr-x 2 ths 512 Apr 22 14:52 complit/ 2 -rw------- 1 ths 1117 Apr 8 1996 travel 2 -rw-r--r-- 1 ths 1609 Feb 13 09:32 team.mmet 2 -rwx--x--x 1 ths 1690 Apr 28 1993 openwin-init* 2 drwx------ 2 ths 1536 Nov 28 1995 html/ 2 drwxr-xr-x 2 ths 1536 Apr 7 12:01 bits2/


Use of Sort:

• Note what happens with some options:host ls -l | sort + 4

total 25

3 -rw------- 1 ths 2238 Jan 29 1992 login.matrix

4 -rw------- 1 ths 3156 Mar 27 1992 file.mat

4 -rw------- 1 ths 3187 Mar 20 1992 mail.mat

7 -rw------- 1 ths 6280 Nov 26 1991 login.bak

7 -rw------- 1 ths 6497 Jan 17 1992 logmatrix.bak


End of Module

Complete Manipulating Files Exercises

june 1, 1999manipulating files1 introduction to unix e. manipulating files

Documents