Advanced Bash-Scripting HOWTO: A guide to shell scripting, using Bash | ||
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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.
1 rm `cat filename` 2 # "filename" contains a list of files to delete. 3 4 textfile_listing=`ls *.txt` 5 # Variable contains names of all *.txt files in current working directory. 6 echo $textfile_listing 7 # 8 textfile_listing2=$(ls *.txt) 9 echo $textfile_listing 10 # Also works. |
![]() | Using backticks for command substitution has been superseded by the $(COMMAND) form. |
1 z=`expr $z + 3` |
1 z=$(($z+3)) 2 # $((EXPRESSION)) is arithmetic expansion. 3 # Not to be confused with command substitution. 4 5 let z=z+3 6 let "z += 3" #If quotes, then spaces and special operators allowed. |