Shell evaluate String Length

$ {# String} $ String Length

$ {String: Position} In $ string , Extract substring from position $ position

$ {String: Position: length} In $ string , Extract substrings with a length of $ length from the position $ position

in shell, sed, expr, and so on can be implemented, the string operation above. Next we will compare the performance.

[chengmo @ localhost ~] $ Test = 'C:/Windows/boot. INI '

[chengmo @ localhost ~] $ Time for I in $ (SEQ 10000); Do A =$ {# test}; done;

real 0m0. 173 S

User 0m0. 139 S

sys 0m0. 004 S

[chengmo @ localhost ~] $ Time for I in $ (SEQ 10000); Do A =$ (expr length $ test); done;

real 0m9. 734 S

User 0m1. 628 S

original:

http://www.cnblogs.com/chengmo/archive/2010/10/02/1841355.html