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. 2020 Apr 15;20:67. doi: 10.1186/s12911-020-1085-4

Table 1.

Examples of Regular Special Symbols and Meaning

Regular symbols Meaning
^ Start position of string
* The front character or expression 0 or more times.
. Any single character other than null
x|y X or Y, where x and y are one or more characters
? Match the previous sub-expression zero or once