expr

Evaluate expressions and manipulate strings. More information: https://www.gnu.org/software/coreutils/expr.

• 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}}