Aritalab:Lecture/NGS/Unix commands - Revision history

Adm: /* Standard Input/Output */

2015-11-09T07:32:22Z

‎Standard Input/Output

Adm at 07:26, 9 November 2015

2015-11-09T07:26:24Z

Adm: /* Standard Input/Output */

2015-11-09T06:06:01Z

‎Standard Input/Output

Adm: /* File Ownership */

2015-11-09T05:58:13Z

‎File Ownership

Adm: /* File operations */

2015-11-09T05:57:42Z

‎File operations

Adm: /* Text Operation */

2015-11-09T05:56:27Z

‎Text Operation

Adm: /* Text Operation */

2015-11-09T05:54:41Z

‎Text Operation

Adm: /* Path and the Current Directory */

2015-11-09T05:52:53Z

‎Path and the Current Directory

Adm: Created page with "==Useful Unix Commands== When you open a terminal, the background "shell" program is already running. It prints out a prompt ">" and parses and executes your input. Famous on..."

2015-11-09T05:49:46Z

Created page with "==Useful Unix Commands== When you open a terminal, the background "shell" program is already running. It prints out a prompt ">" and parses and executes your input. Famous on..."

New page

==Useful Unix Commands==

When you open a terminal, the background "shell" program is already running. It prints out a prompt ">" and parses and executes your input. Famous ones are "bash" (Bourne-again shell) and "tcsh". The shell program offers over 200 commands.

All data in UNIX are organized in a file/directory tree. The entire tree is called the UNIX filesystem.

==File operations==

; ls -l
: Listing all filenames in the current directory. Each line consists of (1) file type and its access permission, (2) number of memory blocks, (3) file owner and group, (4) file size (in bytes), (5) last update time, and (6) file name. To list selected files only, you can use an astarisk * as a don't-care symbol.

; cat ''filename''
:Listing file contents. Option -b attaches line numbers. To see long files, use 'cat ''filename'' | ls'.

{|
|
; cp -i ''from'' ''to'' : Duplicating a file
|
; mv -i ''from'' ''to'' : Renaming a file
|
; rm -i ''filename'' : Deleting a file
|}
:We often mistake the order of ''from'' and ''to'' files in these commands. Therefore, make sure to use the -i option. These commands are destructive and there is no way to undo the operation.

; wc ''filename''
: Counting the line number, word number and file bytes.

====Exercise====

==File Ownership==

When you check files by 'ls -l', you see file permissions. The permission consists of one character showing either it is a file (-) or directory (d), and the three groups of three characters 'rwx'.

Each letter of the three 'rwx' represents read (r), write (w), and execute (x) permission. The first block indicates the permission for the file owner, second block indicates, for group members to which the file belongs, and the last block, for everybody else.

To change permissions, you use the command 'chmod' and a binary notation for the three letter block 'rwx'. For example, the number 6 indicates 'rw-' (read or write permission), the number 4 indicates 'r--' (read only), 7 indicates 'rwx' (all ok). Permissions for the three user types are specified by three consecutive numbers of 0-7.
; chmod 644 'filename'
: Changing the file permission to read only to others. 'chmod 600 ''filename''' makes your file personal.

==Path and the Current Directory==

; cd ''directory''
: When you input commands, the shell executes them from the position you are in. This position is called the current directory, denoted by ' . ' in your commands. You can specify the directory location by .. (one-step down), / (directory), or . (current position). Your home directory is specified as "~/".

At the unix root, you will find the following directories.
:<tt> /bin /sbin /usr /etc </tt>
Bin and sbin are used to store executable files and user files are located in usr. When you type any command, the shell looks for a binary executable file in bin or sbin locations. The places to search is defined as the PATH variable.

Please type 'echo $PATH' to show the PATH value. (The dollar symbol indicates the value of a defined variable and the echo command outputs the input value directly.) You can add a new location to this variable by 'PATH=/usr/bin:$PATH'. In typing this command, do not insert a space such as "PATH = /usr/bin : $PATH'. Space character does matter. OTher important variables include: HOME (home directory), LANG (language switch), and DISPLAY (display identifier).

== Text Operation==

; grep ''pattern'' ''file(s)''
: Searching a regular expression in files. Inputs can be given by other commands through a pipe '|'. Please see its usage by typing 'grep --help'. To fully exploit its power, you need to learn the regular expression.

; sort ''filename''
: Sorting lines of text alphabetically. For a numeric sort, use the '-n' option. To sort by the 2nd or 3rd column, ignore the first N fields by specifying '+N'.

{|
|
; more ''filename''
|  
|
; less ''filename''
|}
: Showing text information page by page. 'More' command can move forward only but 'less' can move backward too. Check their functions by 'more --help', for example.

← Older revision		Revision as of 07:32, 9 November 2015
Line 79:		Line 79:
	Most Unix commands receive a file as their input and the terminal screen as their output. By definition, however, the standard input (stdin) is the keyboard and the standard output (stdout) and the standard error (stderr) are the screen. If you want to change the input/ouput, you can use the notation '>' called redirection.		Most Unix commands receive a file as their input and the terminal screen as their output. By definition, however, the standard input (stdin) is the keyboard and the standard output (stdout) and the standard error (stderr) are the screen. If you want to change the input/ouput, you can use the notation '>' called redirection.

−	For example, if you type '> cat file.txt \| wc > result.txt', then the output of the cat command is fed to the wc command and its standard output (screen) is redirected to the result.txt file.	+	For example, if you type '> cat file.txt \| wc > result.txt', then the output of the cat command is fed to the wc command and its standard output (screen) is redirected to the result.txt file. Conversely, '<' means an input.
		+
		+
		+
		+	==File Compression==
		+
		+	{\|
		+	\|
		+	;tar ztvf ''file''
		+	: Checking the archive table with 't'
		+	\|
		+	;tar zxvf ''file''
		+	: Extracting all files in the archive with 'x'
		+	\|
		+	;tar zcvf ''file.tar.gz'' file1 file2 ...
		+	: Compressing all files with 'c'
		+	\|}
		+	Tar (tape archive) is the most common way to archive files and directories. The second common way is the zip/unzip command.

← Older revision		Revision as of 06:06, 9 November 2015
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	==Standard Input/Output==		==Standard Input/Output==
		+
		+	Most Unix commands receive a file as their input and the terminal screen as their output. By definition, however, the standard input (stdin) is the keyboard and the standard output (stdout) and the standard error (stderr) are the screen. If you want to change the input/ouput, you can use the notation '>' called redirection.
		+
		+	For example, if you type '> cat file.txt \| wc > result.txt', then the output of the cat command is fed to the wc command and its standard output (screen) is redirected to the result.txt file.

@@ Line 62: / Line 62: @@
 ; sort ''file''
 : Sorting lines of text alphabetically. For a numeric sort, use the '-n' option. To sort by the 2nd or 3rd column, ignore the first N fields by specifying '+N'.
 ; cat ''file(s)''
 : Concatenating one or more text files. It outputs the result on the screen, and you can see the file contents. This command is often used with 'more' or 'less' command shown below.
 {|
@@ Line 76: / Line 74: @@
 |}
 : Showing text information page by page. 'More' command can move forward only but 'less' can move backward too. Check their functions by 'more --help', for example.

@@ Line 3: / Line 3: @@
 When you open a terminal, the background "shell" program is already running. It prints out a prompt ">" and parses and executes your input. Famous ones are "bash" (Bourne-again shell) and "tcsh". The shell program offers over 200 commands.
-All data in UNIX are organized in a file/directory tree. The entire tree is called the UNIX filesystem.
+All data in UNIX are organized in a file/directory tree. The entire tree is called the UNIX filesystem. Some examples are shown on [[{{FULLPAGENAME}}/Examples|this subpage]].
 ==File operations==

@@ Line 35: / Line 35: @@
 To change permissions, you use the command 'chmod' and a binary notation for the three letter block 'rwx'. For example, the number 6 indicates 'rw-' (read or write permission), the number 4 indicates 'r--' (read only), 7 indicates 'rwx' (all ok). Permissions for the three user types are specified by three consecutive numbers of 0-7.
-; chmod 644 'filename'
+; chmod 644 'file'
-: Changing the file permission to read only to others. 'chmod 600 ''filename''' makes your file personal.
+: Changing the file permission to read only to others. 'chmod 600 ''file''' makes your file personal.
 ==Path and the Current Directory==

@@ Line 8: / Line 8: @@
 ; ls -l
-: Listing all filenames in the current directory. Each line consists of (1) file type and its access permission, (2) number of memory blocks, (3) file owner and group, (4) file size (in bytes), (5) last update time, and (6) file name. To list selected files only, you can use an astarisk * as a don't-care symbol.
+: Listing all filenames in the current directory. Each line consists of (1) file type and its access permission, (2) number of memory blocks, (3) file owner and group, (4) file size (in bytes), (5) last update time, and (6) file name. To list selected files only, you can use an asterisk * as a don't-care symbol.
-; cat ''filename''
+; cat ''file''
-:Listing file contents. Option -b attaches line numbers. To see long files, use 'cat ''filename'' | ls'.
+:Listing file contents. Option -b attaches line numbers. To see long files, use 'cat ''file'' | ls'.
 {|
@@ Line 19: / Line 19: @@
 ; mv -i ''from'' ''to'' : Renaming a file
+|
-; rm -i ''filename'' : Deleting a file
+; rm -i ''file'' : Deleting a file
 |}
 :We often mistake the order of ''from'' and ''to'' files in these commands. Therefore, make sure to use the -i option. These commands are destructive and there is no way to undo the operation.
-; wc ''filename''
+; wc ''file''
 : Counting the line number, word number and file bytes.
 ====Exercise====
 ==File Ownership==

@@ Line 60: / Line 60: @@
 : Searching a regular expression in files. Inputs can be given by other commands through a pipe '|'. Please see its usage by typing 'grep --help'. To fully exploit its power, you need to learn the regular expression.
-; sort ''filename''
+; sort ''file''
 : Sorting lines of text alphabetically. For a numeric sort, use the '-n' option. To sort by the 2nd or 3rd column, ignore the first N fields by specifying '+N'.
 {|
+|
-; more ''filename''
+; more ''file''
 | &nbsp;
+|
-; less ''filename''
+; less ''file''
 |}
 : Showing text information page by page. 'More' command can move forward only but 'less' can move backward too. Check their functions by 'more --help', for example.

@@ Line 42: / Line 42: @@
 ; cd ''directory''
-: When you input commands, the shell executes them from the position you are in. This position is called the current directory, denoted by ' . ' in your commands. You can specify the directory location by .. (one-step down), / (directory), or . (current position). Your home directory is specified as "~/".
+: When you input commands, the shell executes them from the position you are in. This position is called the current directory, denoted by ' . '. You can check the value of '.' by typing 'pwd' (print working directory).
 At the unix root, you will find the following directories.