Adv command line

Adv command line

//

///math on the terminal...
//evaluating math expressions in the terminal...
expr 1 + 1
//piping the content into bc..
echo "1 + 3 * 12 - 3"| bc
bc

///pushing btw directories
//works like the cd but this one stores the new folder into a stack
pushd /var/some_data
popd 
dirs 	//shows the content of the stack

///metacommands
man pwd
which bc
file afile.ext 		//gives details of this file
file `which vim` 	//the result of the which goes to file
basename 			//return the last part of the path
basename `which nano`
clear 				//same as (ctrl + l)

///file operations
gzip un_fichero.txt 		//
gzip -d un_fichero.txt

//when using > u overwrite the file like in 
ls > out.txt //if u use >> , the content is going to be appended...

#0 stdin //standart input
#1 stdout //standart output
#2 stderr //standart err

//searching in the result of this output..
ls | grep fichero
//when doing 
ls askdjaskd 2> kk.txt 	//u tell the shell to store in kk.txt the error resulting error mesage (the 2 stands for error)
//this is telling the shell to put the errors (&2) in the standart out (&1), all finishing in the same place...
ls INvalid_dir ~ > dirs.txt 2>&1 	//the short way to do this is
ls INvalid_dir ~ &> dirs.txt
//the shell wait for u to put some input (&0)
cat > testing.txt