expr

Evaluate expressions and manipulate strings. More information: https://www.gnu.org/software/coreutils/manual/html_node/expr-invocation.html.

• Get the length of a specific string:

expr length "string"

• Get the substring of a string with a specific length:

expr substr "string" from length

• Match a specific substring against an anchored pattern:

expr match "string" 'pattern'

• Get the first char position from a specific set in a string:

expr index "string" "chars"

• Calculate a specific mathematic expression:

expr expression1 +|-|*|/|% expression2

• Get the first expression if its value is non-zero and not null otherwise get the second one:

expr expression1 \| expression2

• Get the first expression if both expressions are non-zero and not null otherwise get zero:

expr expression1 \& expression2