ls – list directory contents
List information about the files (the current directory by default).
Options :
-a, –all : do not ignore entries starting with . (show hidden files)
-c with -lt : sort by, and show, last modification of file status information.
-h, –human-readable :Â with -l, print sizes in human readable format (e.g., 1K 234M 2G)
-l use a long listing format ( equivalent to ll command)
-r, –reverse : reverse order while sorting
-t sort by modification time
Use cases:
$ ls -lhtr
$ ls -a
$ ll
pwd – print name of current/working directory
Use case:
$ pwd
cd – Change directory
Use cases:
$ cd
$ cd ~
will always put you in your home directory.
$ cd dir
will put you in a subdirectory (dir – directory name)
$ cd ..
will move you up one directory.
$ cd ../../
will move you up two directories.
cp – copy files and directories
Use cases :
$ cp file.txt file_copy.txt copy file.txt contents to file_copy.txt
$ cp file.txt dir/file_copy.txt
$ cp file.txt ../../file_copy.txt
mv – move (rename) files
Use cases:
$ mv file.txt notes.txt
$ mv file.txt dir/subdir/notes.txt
touch – change file timestamps
Use cases:
$ touch file.txt
If file doen’t exists, it will create zero byte file.
cat – concatenate files and print on the standard output
Use cases:
$ cat files.txt
display contents for files.txt
$ cat > files.txt
Override content to files.txt
$ cat >> files.txt
Append content to files.txt
$ cat files.txt >> files2.txt copy files.txt content to files2.txt
mkdir – make directories
Use cases:
$ mkdir mydir
creates mydir directory
$ mkdir -p mydir/notes
creates sub directory in mydir directory
rm – remove files or directories
Use cases:
$ rm files.txt files2.txt
remove files
$ rm -f files.txt files.txt
remove files forcefully.
$ rm -r mydir
remove directories and their contents recursively
rmdir – remove empty directories
Use case:
$ rmdir dir
ln – make links between files
Use cases:
$ ln -s files.txt mydir/files.txt
creates symbolic link (like shortcut files in windows)
$ ln files.txt mydir/notes/files.txt
creates hard link, like another copy of file.
head – output the first part of files
Use cases:
$ head files.txt
outputs first 10 lines
$ head -n files.txt
outputs first n lines
tail – output the last part of files
Use cases:
$ tail files.txt
outputs last 10 lines
$ tail -n files.txt
outputs last n lines
$ tail -30 files.txt | head
$ head -30 files.txt | tail
wc – print newline, word, and byte counts for each file
Use cases:
$ wc -c files.txt
print bytes counts
$ wc -m files.txt
print characters counts
$ wc – l files.txt
print lines counts
$ wc -w files.txt
print word counts
$ wc -L files.txt
print length of the longest line
vi – Visual editor
Use cases:
$ vi files.txt
You we see more info in next chapter.
view – view files as read-only
Use case:
$ view files.txt
more – The more command is a “pager” utility used to view text in the terminal window one page or screen at a time.
Use case:
$ more files.txt
less – opposite of more
Use case
$ less files.txt
date – print or set the system date and time
Use case :
$ date
cal – displays a calendar
Use case:
$ cal
w – Show who is logged on and what they are doing.
Use case:
$ w
locate – find files by name
Use case:
$ locate files.txt
$ locate -i files.txt
ignore case
ps – report a snapshot of the current processes.
Use case:
$ ps -e
To see every process on the system using standard syntax
$ ps axu
To see every process on the system using BSD syntax
top – display Linux tasks
Use cases:
$ top
press q to quit.
kill – terminate a process
Use case:
$ kill pid number
df – report file system disk space usage
Use cases:
df -h
human readable
du – estimate file space usage
Use cases:
$ du -s file
display only a total for each argument
$ du -sh *
display only a total for each file in human readable.
free – Display amount of free and used memory in the system
Use case:
$ free
ssh – OpenSSH SSH client (remote login program)
Use case:
$ ssh username@remotehost
scp – secure copy (remote file copy program)
Use case:
$ scp files.txt user@remotehost:path
man – format and display the on-line manual pages
Use cases:
$ man ls
$ man scp
$ man du
wget – The non-interactive network downloader.
Use case:
$ wget url
su – substitute user
Use case:
$ su – username
substitute other user
$ su –
substitute root user
exit – exit or close terminal
Use case:
$ exit (CRTL -D shortcut)
clear – clear terminal screen
Use case:
$ clear (CTRL +L shortcut)
