expr — stdin stdout  file  opt help version
expr expression
The expr
command does
simple math (and other expression evaluation) on the command
line:
$ expr 7 + 3 10 $ expr '(' 7 + 3 ')' '*' 14 Special shell characters are quoted 140 $ expr length ABCDEFG 7 $ expr 15 '>' 16 0 Meaning false
Each argument must be separated by whitespace. Notice that we
had to quote or escape any characters that have special meaning to
the shell. Parentheses (escaped) may be used for grouping. Operators
for expr
include:
Operator 
Numeric operation 
String operation 


Addition  

Subtraction  

Multiplication  

Integer division  

Remainder (modulo)  

Less than 
Earlier in dictionary. 

Less than or equal 
Earlier in dictionary, or equal. 

Greater than 
Later in dictionary. 

Greater than or equal 
Later in dictionary, or equal. 

Equality 
Equality. 

Inequality 
Inequality. 

Boolean “or” 
Boolean “or”. 

Boolean “and” 
Boolean “and”. 

Does the regular
expression  

Print
 

Return the index of
the first position in string 
For Boolean expressions, the number 0 and the empty string are considered false; any other value is true. For Boolean results, 0 is false and 1 is true. ...
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