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GNU shell utilities

5.4.3 Relations for expr

expr supports the usual logical connectives and relations. These are higher precedence than either the string or numeric operators (previous sections). Here is the list, lowest-precedence operator first.

`|'

Returns its first argument if that is neither null nor 0, otherwise its second argument.

`&'

Return its first argument if neither argument is null or 0, otherwise 0.

`< <= = == != >= >'

Compare the arguments and return 1 if the relation is true, 0 otherwise. == is a synonym for =. expr first tries to coerce both arguments to numbers and do a numeric comparison; if either coercion fails, it does a lexicographic comparison.