Unit 4

Files and Directories

Objectives

After completing this unit, students should be able to:

Describe the different file types

Describe the AIX file system structure

Use full and relative path names in a file specification

Create, delete, and list directories

Use the touch command to create an empty file

A File

A file is:

A collection of data

A stream of characters or a "byte stream"

No structure is imposed on a file by the operating system

File Types

Ordinary:

Text or code data

Directory:

A table of contents, that stores a list of files within thatdirectory

Special Files:

Represent hardware or logical devices

Example: CD-ROM-Device is represented by /dev/cd0

Directory Contents

# type mode links user group date size loc

4 dir 755 2 team01 staff July 10 10:15

512

10 file 644 1 team01 staff July 11 11:00

96

name i-node

subdir1 4

myfile 10

Directory inode Table

Data

$ vi myfile

Hierarchical Structure

/

usr dev home sbin etc var tmp

tty1lp0

suba

.profilemanualstest1

mon_reporttrio_ltrwalrus

team01 team02 team03

test cdoc

creports pgms

binexports

Pathnames

A sequence of file names, separated by slashes (/), that describes the path, the system must follow to locate a file in the file system

Full pathname (start from the /-directory):

/home/team01/doc/mon/report/usr/bin/ls

Relative pathname (start from current directory):

./test1 (. = current directory)

../team03/.profile (.. = parent directory)

Where Am I...?

The print working directory command can be used to find out what your current directory is:

$ pwd

/home/team01

Listing Directories

To list the contents of your current directory:

$ lsc doc manuals test1

To list all files, including hidden (.) files:

$ ls -a. .. .profile c doc manuals test1

To list all files to the end of the directory tree:

$ ls -Rc doc manuals test1

./c:

./doc:mon_report trio_ltr walrus

Syntax : ls [ directory ]

Long Listing of Files

The ls command with the -l option can be used to obtain more information about the files in a directory.

$ ls -ltotal 5drwxrwxr-x 2 team01 staff 1024 Aug 12 10:16 cdrwxrwxr-x 2 team01 staff 512 Feb 18 09:55 doc-rwxrwxr-x 1 team01 staff 320 Feb 22 07:30 suba-rwxrwxr-x 2 team01 staff 144 Feb 22 16:30 test1

$ ls -li test129 -rwxrwxr-x 2 team01 staff 144 Feb 22 16:30 test1

Change Current Directory

Move from directory /home/team01 to /home/team01/doc:

$ cd doc relative path

$ cd /home/team01/doc full path

Move to your home directory:

$ cd

Move to the parent directory:

$ cd ..

Syntax : cd [ directory ]

To create the directory test, as a sub-directory of /home/team01:

$ mkdir /home/team01/test full path name

(or)

$ cd /home/team01

$ mkdir test relative path name

Creating Directories

Syntax : mkdir directory

Activity: Q + A

1. How can you determine the inode number of a file ?

2. Where are the names and inode numbers of files stored ?

3. How can you determine your current directory ?

4. How can you list all files in a directory, including hidden files ?

5. Your current directory is /usr/dt/bin. What is the easiest way to change to your home directory ?

6. Which filenames are relative ?

../team03/dir1 :/tmp/file1 :/.profile :./.profile :

7. Write down the three different file types that AIX knows:a)b)c)

Removing Directories

Remove the directory /home/team01/doc:

$ rmdir /home/team01/doc

Syntax : rmdir directory

The directory must be empty !

$ rmdir books

rmdir: books not empty

Create multiple directories simultaneously:

$ mkdir -p dir1/dir2/dir3

Remove a directory and all its subdirectories:

$ rmdir -p dir1/dir2/dir3

Working with Multiple Directories

home

/

team01

dir1

home

/

team01

dir2

dir3

Displaying Directory Information

$ ls -ldi mydir

51 drwxr-xr-x 2 team01 staff 512 Jan 17 17:38 mydir

$ istat mydir

Inode 51 on device 10/8 Directory

Protection: rwxr-xr-x

Owner: 208(team01) Group: 1 (staff)

Link count: 2 Length 512 bytes

Last updated: Mon Jan 17 21:05:43 2000

Last modified: Mon Jan 17 17:38:52 2000

Last accessed: Tue Jan 18 13:30:00 2000

AIX Filenames

Should be descriptive of the content

Should use only alphanumeric characters:UPPERCASE, lowercase, number, #, @, _

Should not include imbedded blanks

Should not contain shell metacharacters:* ? > < / ; & ! [ ] | $ \ ' " ( )

Should not begin with "+" or "-" sign

Should not be the same as a system command

Are case sensitive

Filenames starting with a . (dot) are hidden from the normal ls command

The maximum number of characters for a filename is 255

touch Command

The touch command updates the access and modification times of a file. The command can also be used to create zero-length files.

$ ls -l-rwxrwxr-x 1 team01 staff 320 Jan 6 07:30 suba

$ dateThu Sep 10 12:25:00 2000

$ touch suba new_file

$ ls -l -rwxrwxr-x 1 team01 staff 320 Sep 10 12:25 suba-rw-r--r-- 1 team01 staff 0 Sep 10 12:25 new_file

Next Step ...

Exercise 3

Unit 4: Checkpoint

1. Using the tree structure shown earlier, and using /home as your current directory, how would you refer to the suba file in the pgms directory using both full and relative path names? ____________________________________________________ ____________________________________________________

2. When specifying a path name, what is the difference between the . and the ..? ____________________________________________________ ____________________________________________________

3. What will the cd ../.. command do? ____________________________________________________ ____________________________________________________

4. What conditions have to be satisfied in order for the rmdir command to complete successfully? ____________________________________________________ ____________________________________________________

Unit 4: Checkpoint (Cont)

5. Match the various options of the ls command with their functions.

a. -a __ Provides a long listing of filesb. -i __ Will list hidden filesc. -d __ List subdirectories and their contentsd. -l __ Displays the inode numbere. -R __ Displays information about a directory

6. Which of the following are valid filenames.a. 1b. aBcDec. -myfiled. my_filee. my.filef. my fileg. .myfile

Summary

There are three types of files which are supported:OrdinaryDirectorySpecial

The AIX file system structure is a hierarchical tree

Files are accessed using either full or relative path names. A full path name always begins with a / (forward slash)

The following commands can be used with directories: pwd, cd, mkdir, rmdir and ls