File: coreutils.info,  Node: Relations for expr,  Next: Examples of expr,  Prev: Numeric expressions,  Up: expr invocation

16.4.3 Relations for ‘expr’
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‘expr’ supports the usual logical connectives and relations.  These have
lower precedence than the string and numeric operators (previous
sections).  Here is the list, lowest-precedence operator first.

‘|’
     Returns its first argument if that is neither null nor zero,
     otherwise its second argument if it is neither null nor zero,
     otherwise 0.  It does not evaluate its second argument if its first
     argument is neither null nor zero.

‘&’
     Return its first argument if neither argument is null or zero,
     otherwise 0.  It does not evaluate its second argument if its first
     argument is null or zero.

‘< <= = == != >= >’
     Compare the arguments and return 1 if the relation is true, 0
     otherwise.  ‘==’ is a synonym for ‘=’.  ‘expr’ first tries to
     convert both arguments to integers and do a numeric comparison; if
     either conversion fails, it does a lexicographic comparison using
     the character collating sequence specified by the ‘LC_COLLATE’
     locale.