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DOS批处理 & 脚本技术（批处理室） » Ask: How to judge that the input variable is empty.

Floor16　3742668	Posted 2006-12-11 07:02
荣誉版主　Posts 718　Credits 2,013
It is recommended to use the format if defined varName to judge whether a variable is empty, because in many cases, the judgment of if "var" == "" may be wrong due to the variable containing special values.

Floor17　yardian	Posted 2006-12-12 01:59
中级用户　Posts 85　Credits 305
The method above can only judge whether the variable exists, but it seems it can't judge whether the variable is empty. I tried: set B= if defined B (echo B dump) else (echo full) The result shows full. Can you explain it in detail?

Floor18　9527	Posted 2006-12-12 02:14
银牌会员　Posts 438　Credits 1,185　From 北京
defined is to determine whether a variable is defined, regardless of its value. The test result of the upstairs was originally correct. @echo off&setlocal set b=hello set b if defined b (echo YES) else (echo NO) pause set b= set b if defined b (echo YES) else (echo NO) pause

Floor19　ccwan	Posted 2006-12-12 02:16
金牌会员　Posts 1,160　Credits 2,725　From 河北廊坊
So it turns out that Brother 9527 has joined KFC! ^_^

Floor20　yardian	Posted 2006-12-12 02:23
中级用户　Posts 85　Credits 305
Originally posted by 9527 at 2006-12-12 02:14 AM: defined is to determine whether a variable is defined, regardless of what value it has. The test result of the upstairs is originally correct @echo off&setlocal set b=hello set b if defined b (echo YES) else (echo NO) p ... Mistakenly reversed the echo.

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