Shulou(Shulou.com)06/03 Report--

Example 1: tested by the `date` command in backquotes

[root@XCN ~] # echo '`date`' `date` # what you see in single quotes [root@XCN ~] # echo "`date`" Fri Jun 16 14:45:29 CST 2010double quotes if it is a variable, it will first parse the variable into the specific content in the display [root@XCN ~] # echo `date` Fri Jun 16 14:46:49 CST 2011generally do not add quotation marks for consecutive strings, it is generally safe to add double quotation marks It is recommended that [root@XCN ~] # echo $(date) Fri Jun 16 14:48:45 CST 2011uses () to print command input.

Example 2: test when calling after the variable is defined

[root@XCN ~] # xcn=dobe # create a variable without quotation marks [root@XCN ~] # echo $xcn # without quotation marks, display the parsed content of a variable dobe [root@XCN ~] # echo'$xcn' # single quotation marks, display a variable itself $xcn [root@XCN ~] # echo "$xcn" # double quotes, display the content of a variable, and the quotation marks can be variables, strings, etc.

Example 3:grep filter string example

[root@XCN ~] # cat > grep.logbodoxcn [root@XCN ~] # cat grep.logbodoxcn [root@XCN ~] # grep'$xcn' grep.log

Special example: example of awk calling shell variable quotation marks

[root@XCN ~] # XCN=123 [root@XCN ~] # awk 'BEGIN {print "$XCN"}' $XCN [root@XCN ~] # awk 'BEGIN {print' $XCN'} '123 suggests that the above results are exactly the opposite of the previous conclusion. This is a special use of awk calling shell variables

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.