Linux expr command

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The expr command is a manual command-line counter used in UNIX/To get the value of an expression variable under LINUX, it is generally used for integer values, and can also be used for strings.

Syntax

expr Expression

Expression Description:

• Items are separated by spaces;

• Use the backslash \ before shell-specific characters;

• Strings containing spaces and other special characters should be enclosed in quotes

Online Examples

1Calculate the length of the string

> expr length "this is a test"
　14

2Extract the string

> expr substr "this is a test"　3　5
is is

3Find the position of the first occurrence of the character string

> expr index "sarasara" a
　2

4Integer Arithmetic

　> expr　14　%　9
　5
　> expr　10　+　10
　20
　> expr　1000　+　900
　1900
　> expr　30　/　3　/　2
　5
　> expr　30 \*　3　(When using the asterisk, it must be escaped to avoid its special meaning. Because the shell may misunderstand the meaning of the asterisk.)
　90
　> expr　30　*　3
　expr: Syntax error

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