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Help on Command.
man <cmd> 
Type man ls to read the manual for the ls command 
Navigate between Directories
ls -ltrah <path>
List contents of the directory <path> including entries starting with `.` in the long listing format with human readable size like 2G rather than

2146858929 and sorted by their modification date, oldest first.

cd <path>

Change the current directory to <path>

pwd 
Show the absolute path of the current directory
Special Directories
Home directory
Current directory
.. 

Parent directory

Modify  Directories
mkdir -p <path> 
Make a new directory with the path <path>. Missing parent directories along the path will be created.
cp <file> <dst> 
Copy the file <file> to  the destination <dst>. If <dst> is a directory, the new file will be created inside it.
cp -r <dir1> <dir2> 
Copy directory dir1 and all its contents recursively as/to <dir2>. If <dir2> exists, the new directory will be created inside <dir2>.
mv <file> <dst> 
Move the file <file> to the destination <dst>. If <dst> is a directory, the file will be moved inside it.
rm <file>
Remove files. “?” is any character; “*” is any string of characters. 
rm -rf <dir>
USE WITH CAUTION. Remove all contents of the directory <dir> recursively and forcefully. 
Connect/Copy files to remote host
ssh <user>@gadi.nci.org.au 
Login to Gadi as the user <user>
scp <file> <user>@gadi-dm.nci.org.au:<dst> 
Copy local <file> to Gadi into the directory <dst> or as the file <dst> 
View/Edit a Text File
less <file> 
View <file> with less 
cat <file> 
Print <file> on screen
vim <file> 
Edit <file> with vim 
emacs <file> 
Edit <file> with emacs 
Compress files
tar czf file.tar.gz <folder> 
Create the compressed archive <file.tar.gz> with gzip for all contents in the folder <folder> (use xzf to extract) 
gzip <file> 
Compresses file and renames it to file.gz 
Other Useful Commands
diff -y <file1> <file2> 
Show the differences between <file1> and <file2> side-by-side 
grep -n "str" <file> 
Print lines containing the string str in <file> with the prefix of its line number 
awk -F, '{print $4}' <file> 
Print the 4th column of the file <file> using comma as the field separator 
wc -l <file> 
Count lines in the file <file> 
find <path> -type d -name *1234*
Search through the directory <path> for directories with name containing the string 1234
File Access Permissions
chmod g+w <file>
Add group writable permission to the file <file>
chgrp -R <prj> <path>
Set the owner group of the directory <path> and its contents to the project <prj> recursively.
getfacl <file>
Get file access control lists of the file <file>
Pipes and Redirection
ls -l > list.txt 
List the content of the current directory and redirect the output to the file list.txt. If file list.txt exists, overwrite it with the output.
<cmd> >> <file> 
Append output of the command <cmd> to the file <file>
<cmd> < <file> 
Get input of the command <cmd> from the file <file>
<cmd1> | <cmd2> 
Pipe the output of command <cmd1> to the standard input of command <cmd2>
Shortcuts
Ctrl+C 
Halt the current command
Ctrl+A
Move cursor to the beginning of the line
Ctrl+E
Move cursor to the end of the line
Ctrl+K

Delete from cursor to the end of the line

Ctrl+Z 
Stop the foreground job and places it in the background as a stopped job
Ctrl+D 
Log out of current session, similar to exit