coreutils: Standards conformance

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1 2.13 Standards conformance
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1 
1 In a few cases, the GNU utilities’ default behavior is incompatible with
1 the POSIX standard.  To suppress these incompatibilities, define the
1 ‘POSIXLY_CORRECT’ environment variable.  Unless you are checking for
1 POSIX conformance, you probably do not need to define ‘POSIXLY_CORRECT’.
1 
1    Newer versions of POSIX are occasionally incompatible with older
1 versions.  For example, older versions of POSIX required the command
1 ‘sort +1’ to sort based on the second and succeeding fields in each
1 input line, but in POSIX 1003.1-2001 the same command is required to
1 sort the file named ‘+1’, and you must instead use the command ‘sort -k
1 2’ to get the field-based sort.  To complicate things further, POSIX
1 1003.1-2008 allows an implementation to have either the old or the new
1 behavior.
1 
1    The GNU utilities normally conform to the version of POSIX that is
1 standard for your system.  To cause them to conform to a different
1 version of POSIX, define the ‘_POSIX2_VERSION’ environment variable to a
1 value of the form YYYYMM specifying the year and month the standard was
1 adopted.  Three values are currently supported for ‘_POSIX2_VERSION’:
1 ‘199209’ stands for POSIX 1003.2-1992, ‘200112’ stands for POSIX
1 1003.1-2001, and ‘200809’ stands for POSIX 1003.1-2008.  For example, if
1 you have a POSIX 1003.1-2001 system but are running software containing
1 traditional usage like ‘sort +1’ or ‘tail +10’, you can work around the
1 compatibility problems by setting ‘_POSIX2_VERSION=200809’ in your
1 environment.
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