Here our requirement is to remove all the whitespace from the leading and ending space per line of a file.
Our sample file /tmp/file
This is line one
This is line two
This is line three
This is line four
Remove all leading whitespace
To remove all tab whitespace (This will not remove empty space)
# sed 's/^[ ]\*//g' /tmp/file
This is line one
This is line two
This is line three
This is line four
As you see the "tab" space is still there
To remove all leading whitespaces (including tabs)
# sed 's/^[t ]\*//g' /tmp/file
This is line one
This is line two
This is line three
This is line four
Remove all trailing whitespace
To remove all trailing whitespaces (including tabs)
# sed -i 's/[t ]\*$//g' /tmp/file
Remove both leading and trailing whitespaces
# sed 's/^[t ]\*//g;s/[t ]\*$//g' /tmp/file
This is line one
This is line two
This is line three
This is line four
Here I have combined both the commands with ";"