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| File Managment
Commands |
|---|
| cat | Join files or display them
Read one or more files and print them on the screen (or
standard output). You can then use the > operator to
combine several files into a new file.
Examples:
| cat
hello.txt | Displays the file
hello.txt |
| cat hello.txt world.txt >
helloworld.txt | Combines files hello.txt and
world.txt into one file called helloworld.txt |
| | cd | Change working directory
Examples:
| cd | Changes working
directory to user's home directory. |
| cd dir1 | Changes
working directory to dir1. |
| cd .. | Changes
working directory one level up. |
| | chmod | Change access modes on files
Only the owner of a file or a privileged user may change its mode.
Syntax: chmod [option] mode files
Options: -R Recursively descend thgrough directoy setting modes to files
Mode: Composed of who, opcode and permission.
| Who | u | User |
| g | Group |
| o | Other |
| a | All (default) |
| Opcode | + | Add permission |
| - | Remove permission |
| = | Assign permission (and remove permission of the unspecified fields) |
| Permission |
r | Read | OR* | 4 | Read |
| w | Write | 2 | Write |
| x | Execute | 1 | Execute |
*Permissions may also be specified by a 3 digit sequence.
The first digit designates owner permission; the second, group permission; and the
third, others permission. Permissions are calculated by adding the values in the table.
Examples:
| chmod u+x file | Adds execute-by-user permission to file |
chmod 751 file
chmod u=rwx,g=rx,o=x file |
Both these examples assign read-write-execute permission by owner (7),
read-write permission by group (5), and execute-only permission by others (1) to
file. |
| | cp | Copy files
Syntax: cp [options] file1 file2
cp [options] files directory
Examples:
| cp file1 file2 | Copies file1 into file2. |
| cp file1 file2 file3 dir1 |
Copies file1, file2 and file3 to directory dir1, preserving the files' names |
| cp -r dir1 dir2 | Recursivle copy directory dir1, its files and
subdirectories to a destination directory dir2 (duplicating the tree structure). |
| | head | Show the first few lines of a file
Examples:
| head -20 file1 | Displays the first 20 lines of file1 |
|
| ls | List files or directories
Syntax: ls [options] [names]
If no names are given, list the files in the current directory. With one or more names, list files contained in a directory name or that match a file name.
Some Options:
| -a | List all files, including the normally hidden . files |
| -c | List files by creation/modification time |
| -l | Long format listing (includes permissions, owner, size, modification time, etc.) |
| | mkdir | Create a directory
Syntax: mkdir directories
Create one or more directories. You must have write permission in the parent
directory in order to create a directory.
Examples:
| mkdir dir1 | Creates a directory named dir1. |
| mkdir dir1 dir2 dir3 | Creates directories named dir1, dir2 and dir3. |
|
| more | Display files by screenful
Syntax: more files
Display the named files on a terminal, one screenful at a time.
After each screen is displayed, press RETURN to display the next
line or press the spacebar to display the next screenful.
| | mv | Move or rename files or directories
Syntax: mv sources target
Basic command to move files and directories around on the system or to rename them.
The following table summarizes how mv works.
| | pwd | Print your working directory | | rm | Remove files | | rmdir | Remove directories | | tail | Show the last few lines of a file | | wc | Count lines, words, and characters | | Back to top |
| Miscellaneous Commands |
|---|
| bc | Precision calculator
Input can
be taken from files or read from the standard input. To exit,
type "quit" or "EOF".
For mor information type "man
bc". | | cal | Display calendar
With no arguments, cal prints the calendar for
the current month. Otherwise, print either a 12-month
calendar (beginning with January) for the given
year or a one-month calendar of the given
month and year.
Examples:
| cal 10
2003 | Displays one-month calendar for
October, 2003 |
| cal 2005 | Displays 12-month
calendar for 2005 |
| | clear | Clear the screen | | man | Display information from the on-line reference manuals.
Syntax: man [command]
Example: man mkdir Display manual pages for command "mkdir". | | tar | Tape archiver
Syntax: tar [options] [files]
Copy files to or restor files from tape. If any files are directories, tar acts on the entire
subtree.
| Options | -zcvf arch | Create a new tape arch. |
| -ztvf arch | Print names of files in arch. |
| -zrvf arch | Append files to tape arch. |
| -zxvf arch | Extract files from tape arch. |
Examples:
| tar -zcvf arch file1 file2 | Creat an archive of file1 and file2
and store it in arch |
| tar -zxvf arch | Extract all the files in arch. |
| | vi | Visual text editor
Syntax: vi [file]
If file exists, open file for editting. Otherwise, create file and open for editing.
If no file is specified, vi opens wiht an empty buffer.
Some vi commands:
| a | Append after the cursor. |
| A | Append at end of line. |
| i | Insert before cursor. |
| I | Insert at beginning of line. |
| o | Open a line below current line. |
| O | Open a line above current line. |
| dd | Delete current line. |
| :w | Write to file. (use :w! to force write) |
| :q | Quit vi. (use :q! to force quit) |
| h | Move one character to the left. |
| j | Move one line down. |
| k | Move one line up. |
| l | Move one character to the right. |
| | Back to top |
| System
Status Commands |
|---|
| chgrp | Change file group
Syntax: chgrp [options] newgroup files
Change the ownership of one or more files to newgroup.
You must own the file or be a privileged user to suceed this command.
Example:
| chgrp hello.txt group1 | Changes the group for file hello.txt to group1 |
| chgrp -R dir1 group1 | Recursively descends through directory dir1, including subdirectories, setting group to group1 |
| | chown | Change file owner
Syntax: chown [options] newowner files
Change the ownership of one or more files to newowner.
Example:
| chown user1 file1 file2 |
Changes the owner of file1 and file2 to user1. |
| chown -R user1 dir1 |
Recursively descends through directory dir1, including subdirectories, setting
the owner to user1. |
| | date | Display the current date and time.
Priviledged users may also set a date and time. | | finger | Point out information about users.
Syntax: finger [options] users
Displays data about one or more users. | | hostname | Print the name of the host machine. | | ps | Report on active processes
Syntax: ps [options]
| Options | -A | List all processes. |
| -u users | List processes only for usernames in users. |
For more options type man ps.
| | who | List the names of users currently
logged into the system. | | whoami | Print the effective username. | | Back to top |
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