Sun Fundamentals of Solaris 7 EU-118 Student Guide With Instructor Notes phần 5 doc

Enterprise Services August 1999, Revision D Upon completion of this module, you should be able to ● Control screen output using control characters ● Determine a file’s type with thefilec

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Upon completion of this module, you should be able to

● Control screen output using control characters

● Determine a file’s type with thefilecommand

● Display the contents of text files using the cat,more,head, and

tailcommands

● Determine word, line, and character count using the wccommand

● Compare the contents of text files using diffand cmp

● Create empty files or update access time of existing files using the

touchcommand

● Create and remove directories using mkdirand rmdir

● Manage files and directories using the mv,cp, and rmcommands

● Save the output from a command into a file

● Pass output from one command to another using a pipe

● Use theteecommand within a pipeline to create text within a file

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Relevance

✓ Present the following question to stimulate the students and get them thinking about the issues and topics presented in this module While they are not expected to know the answer to the question, the answer should be of interest to them and inspire them to learn the content presented in this module.

Discussion – What tasks do you need to complete to manage your

files and directories?

Additional Resources

Additional resources – The following reference can provide additional

details on the topics discussed in this module:

● Solaris User’s Guide, Part Number 802-6499

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Directory and File Commands 6-3

Control Characters

Control characters are used to perform specific tasks such as stoppingand starting screen output When displayed on the screen, the Controlkey is represented by the caret symbol (^)

To enter a sequence of control characters, hold down the Control keyand press the appropriate character on the keyboard

✓ The Control-s and Control-q characters were originally needed by teletype operators and are rarely used today.

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Control Characters

The following control characters can be used:

✓ The actual character in the shell appears as^C, even though you press the Control key and the c key at the same time.

Table 6-1 Control Characters

Control Characters Purpose

Control-s Stops screen outputControl-q Resumes screen outputControl-c Interrupts current activityControl-d Indicates end-of-file or exitControl-u Erases the command lineControl-w Erases the last word on the line

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Determining File Type

There are many types of files found on a Solaris system The type offile can be determined by using the filecommand This informationcan be important when a user is attempting to open or read a file.Determining the file type can help a user decide which program orcommand to use to open the file

The output from this command will most often be one of thefollowing:

● Text – Examples include ASCII text, English text, commands text,

and executable shell scripts The text file type also includesexecutable shell scripts This type of file can be read using thecat

ormorecommands, which are discussed in this module, andedited usingvior another editor

✓ The filecommand determines file type by referencing the first two bytes of the file See the contents of /etc/magic.

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Determining File Type

● Executable or Binary – Examples include 32-bit executable and

extensible linking format (ELF) code files and other dynamicallylinked executables This file type indicates that the file is acommand or program Thestringscommand, shown on the nextpage, will print out readable characters in this type of file (Theoutput produced bystringsis easily interpreted by someonewith a programming background The command is introducedhere solely as a method for demonstrating the printable characters

of an executable file.)

● Data – Data files are those which are created by an application

running on the system In some cases the type of file is indicated;for example, FrameMaker document When the application inwhich this file was created cannot be determined by thefile

command, the output will simply indicate data file The only way

to read a data file is to determine which application created it andopen the document with that application If you have manyapplications on your system, this can be a time consumingprocess

For information on other file types, see the man pages

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Example Data File

$ cd /home/user2/dir1/coffees

$ file beans

FrameMaker must be used to read the beansfile

Example Executable File

$ strings /usr/bin/cat

SUNW_OST_OSCMDusvtebn

usage: cat [ -usvtebn ] [-|file]

cat: Cannot stat stdoutcat: cannot open %scat: cannot stat %scat: input/output files ‘%s’ identicalcat: close error

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Displaying Files

Using the cat Command

Thecat(concatenate) command displays the contents of a text file onthe screen It is often used to display short text files; becausecat

flashes through the entire file rapidly without pausing, it is unsuitablefor files longer than one screen in length Thecatcommand is moreoften used to join two or more files into one large file

Command Format

cat filename(s)

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Using the cat Command

Using the cat Command to Display a Short Text File

$

If the file fills more than one screen, the data scrolls off the screen—unless you are using a scrolling window, such as a terminal window,within the CDE environment

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Displaying Files

Using the more Command

Use themorecommand to display the contents of a text file to thescreen one screen at a time If the information in a file is longer thanone screen, the following message appears at the bottom of the screen:

More (n%)

where n is the percentage of the file already displayed.

The on-line manual pages use themoreutility for display purposes, sothe scrolling keys in the following table are the same ones you used todisplay man pages

Note – Usingcatormoreto read executable or binary files can cause

a terminal or window to hang

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Using the more Command

Command Format

more filename(s)

At the More prompt, you can use the following keys to control thescrolling capabilities:

Table 6-2 Scrolling Keys

Scrolling Keys Purpose

Spacebar Scroll to the next screenReturn Scroll one line at a time

b Move back one screen

f Move forward one screen

h Display a Help menu ofmore features

q Quit and return to the shell prompt

/string Search forward forstring

n Find next occurrence ofstring

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Displaying Files

Using the head Command

Use theheadcommand to display the first n lines of one or more files.

The first 10 lines are displayed by default if the-noption is omitted

Command Format

head [ -n ] filename(s)

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Using the head Command

Displaying a Specific Number of Lines at the Beginning of a File

$ head -6 /usr/dict/words

10th1st2nd3rd4th5th

$

In this example, the head -6command displays the first six lines ofthe /usr/dict/wordsfile

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Displaying Files

Using the tail Command

Use thetail command to display the last n lines of a file The last 10

lines are displayed by default if the-noption is omitted

Command Format

tail [ -n ] filename(s)

tail [ +n ] filename(s)

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Using the tail Command

Displaying a Specified Number of Lines at the End of a File

$ tail -5 /usr/dict/words

zoundsz‘szucchiniZurichzygote

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Displaying Files

Using the wc Command

Use thewccommand to display a line, word, or character count of afile This command is useful when trying to determine characteristics

of a file Whereas the size can be determined in bytes by using the

ls -lcommand, much more information is obtained with wc

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Using the wc Command

Using wc Without Options

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Comparing Files

Locating Text Differences With the cmp Command

Comparing files to determine differences between them can be doneusing thecmpcommand This command produces no output if thefiles are exactly the same, or it provides the byte and line numbers atwhich the first difference occurred if there are discrepancies betweenthe files

Command Format

cmp file1 file2

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Locating Text Differences With the cmp Command

Using the cmp Command to Compare Files That Appear to be the Same

You would:

1 Do a long listing and compare the file sizes

-rw-r r 1 user2 edu 3528 July 6 16:19 /home/user2/cshrc-rw-r r- 1 user2 edu 3528 July 6 16:19 /home/user2/.cshrc

2 From the long listing, identify the date the files were last changed

If this date signifies that the files are the same, use thecmp

command

$ cmp ~/cshrc ~/.cshrc

cshrc /home/user2/cshrc differ: char 1638, line 42

This output identifies the first occurrence of a difference betweenthe two files The difference occurred at the 1,638th characterposition and was found on line 42

You can now manually locate any further discrepancies and takewhatever action you deem necessary

Note – The cmpcommand is quite useful when comparing binary files,but less useful for text files For more information on this command,see the man pages

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Comparing Files

Using the diff Command

Another command used for finding differences between files is the

diffcommand The output of this command will display line-by-linedifferences between two text files

Command Format

$ diff [option] file1 file2

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Options

-i Ignores the case of letters; for example, A is equal to

a

-c Produces a listing of differences with three lines of

context With this option, output format is modifiedslightly: output begins with identification of thefiles involved and their creation dates Following aline of a dozen *s, the line numbers offile1 thatare to be displayed are listed The actual lines from

file1 are then displayed, appended by a – forthose lines that are different fromfile2 The samedisplay follows as it applies tofile2, with a +appended for those lines that are different from

file1

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Comparing Files

Using diff to Compare Files

$ diff -c fruit fruit2

*** fruit Fri May 8 11:32:49 1998 - fruit2 Fri May 8 14:55:21 1998

************

***2, 8****

orangeapplebanana-pear-mangotomatopomegranate -2, 8 orangeapplebananatomato+guava+mangopomegranate

$ cat fruit

lemonorangeapplebananapearmangotomatopomegranate

$ cat fruit2

lemonorangeapplebananatomatoguavamangopomegranate

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File and Directory Naming Conventions

● File names may contain one or more extensions, usually appended

to file by an application Extensions are usually one to three

characters that are appended to the end of a file name and arepreceded by a period (.) You may choose to use this conventionwhen naming files, but it is not a necessary part of a file name

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File and Directory Naming Conventions

● Directory names generally do not contain extensions, but there are

no rules against it

Note – To help distinguish between files and directories, some site

administrators prefer their users to start filenames with lowercaseletters and directory names with capital letters

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Creating Empty Files

Note – The touchcommand creates an empty file if the file namespecified does not exist Otherwise, the access/modification time ofthe existing file is updated

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Suppose you want to create a file which contains the names and phonenumbers of your co-workers You can use theteecommand as

follows:

$tee phone_list.txt Bill O - 808-555-9876

Bill O - 808-555-9876

Fred P - 808-555-6543

Fred P - 808-555-6543

^D

When the first line is entered, the system searches for a file named

phone_list.txt.If the file exists, the system overwrites its contentswith the new information If the file does not exist, it is created and thecontent is written into it

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Each line is entered by pressing the Return key The line of text isduplicated in the shell, showing you it has been written to the outputfile Use Control-d to end the input of content

The -a option for theteecommand allows you to append to a file’scurrent contents without overwriting the current contents

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Creating Directories

Use themkdircommand to create directories Directories can becreated using either an absolute or a relative pathname You canspecify more than one directory name on the same line to create morethan one new directory

Command Format

mkdir [-p] directory_name

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Creating Directories

You must have the appropriate permissions to create a directory.(Permissions are covered later in the course.) If you do not have thecorrect permissions on a file or directory, you will receive an errormessage similar to this one:

You can create multiple levels of directories at one time by using the

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Copying Files

Use the cpcommand to copy files

Command Format

cp [-i] source_file destination_file

cp [-i] source_file(s) destination_directory

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Copying Files

Copying a File to Another Within a Directory

The following example demonstrates how to copy one file to a new file

in the same directory:

$ cp feathers feathers_6

Copying Multiple Files

The following example demonstrates how to copy multiple files into adirectory other than the current directory:

$ pwd

/home/user2

$ ls dir1

coffees fruit trees

$ cp feathers feathers_6 dir1

$ ls dir1

coffees feathers feathers_6 fruit trees

Preventing Overwriting an Existing File When Copying

Usecp -i as a security measure The-ioption prompts you if youare about to overwrite an existing file

$ cp -i feathers file3 cp: overwrite file3 (yes/no)? n

$

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Copying Directories

Use the cp -r(recursive) command to copy a directory and itscontents to another directory If the directory does not exist, it iscreated by the cpcommand

Command Format

cp -r[i] source_directory(s) destination_directory

Without the-roption, the files and subdirectories contained within adirectory are not copied When used with the -ioption,cppromptsfor verification before overwriting an existing file

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