Linux is a name that broadly denotes a family of free and open-source software operating systems built around the Linux kernel. Typically, Linux is packaged in a form known as a Linux distribution for both desktop and server use. Linux works on command line interface (CLI) i.e. most of the work done in Linux is done by typing some set commands on the terminal. Here are a few of those commands which will help you to begin on Linux.
Terminal Control Characters
^h backspace erase previously typed characters
^u erase entire line of input so far typed
^d end-of-input for programs reading from terminal
^s stop printing on terminal
^q continues printing on terminal
^z currently running job; restart with bg or fg
DEL, ^c kill currently running program and allow clean-up before exiting
^\ emergency kill of currently running program with no chance of clean-up
Login and Authentication
login access computer; start interactive session
logout disconnect terminal session
passwd change local login password; you MUST set a non-trivial password Information
date show date and time
history list of previously executed commands
pine send or receive mail messages
msgs display system messages
man show on-line documentation by program name
info on-line documentation for GNU programs
w, who who is on the system and what are they doing
who am i who is logged onto this terminal
top show system status and top CPU-using processes
uptime show one line summary of system status
finger find out info about a user@system
File Management
cat combine files
cp copy files
ls list files in a directory and their attributes
mv change file name or directory location
rm remove files
ln create another link (name) to a file
chmod set file permissions
des encrypt a data file with a private key
find find files that match specified criteria
locate finds all the files on the file system, starting at the root, that contain all or any part of the search criteria
Display Contents of Files
cat copy files to display device
vi screen editor for modifying text files
more show text file on display terminal with paging control
head show first few lines of a file(s)
tail show last few lines of a file; or reverse line order
grep display lines that match a pattern
lrp send files to line printer
pr format files with page headers, multiple columns etc.
diff compare two files and show differences
cmp compare two binary files and report it differently
od display binary file as equivalent octal/hex codes
file examine file(s) and tell you whether text, data, etc.
wc count characters, words, and lines in a file
Directories
cd change to new directory
mkdir create new directory
rmdir remove empty directory (remove files first)
mv change name of directory
pwd show current directory
Devices
df summarize free space on disk device
du show disk space used by files or directories
Special Character Handling for C-shell
* match any character in a file name
~user shorthand for home directory of “user”
$name substitute value of variables “name”
\ turn off special meaning of character that follows
‘ In pairs, quote string with special chars, except !
“ In pairs, quote string with special chars, except !, $
` In pair, substitute output from enclosed command
Controlling Program Execution for C-shell
& run job in background
DEL, ^c kill job in foreground
^z suspend job in foreground
fg restart suspended job in foreground
bg run suspended job in background
; delimit commands on same line
() group commands on same line
! re-run earlier commands from history list
ps print process status
kill kill background job or previous process
nice run program at lower priority
at run program at later time
crontab run program at specified intervals
limit see or set resource limit for programs
alias create alias name for program (in .login)
sh, csh execute command file
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