Commands within backticks generate command line text.
The output of commands within backticks can be used
as arguments to another command or to load a variable.
rm `cat filename`
# "filename" contains a list of files to delete.
textfile_listing=`ls *.txt`
# Variable contains names of all *.txt files in current working directory.
echo $textfile_listing
#
textfile_listing2=$(ls *.txt)
echo $textfile_listing
# Also works.
Note: Using backticks for command substitution has been
superseded by the $(COMMAND)
form.
Arithmetic expansion (commonly used with
expr)
z=`expr $z + 3`
Note that this particular use of backticks
has been superseded by double parentheses
$((...)) or the very convenient
let construction.
z=$(($z+3))
# $((EXPRESSION)) is arithmetic expansion.
# Not to be confused with command substitution.
let z=z+3
let "z += 3" #If quotes, then spaces and special operators allowed.
All these are equivalent. You may use whichever one
"rings your chimes".
