tail +n is a obsolete syntax, and was deprecate in POSIX 1003.1-2001. >From the coreutils manual:
| Standards conformance | ========================== | | In a few cases, the GNU utilities' default behavior is incompatible | with the POSIX standard. To suppress these incompatibilities, define | the `POSIXLY_CORRECT' environment variable. Unless you are checking | for POSIX conformance, you probably do not need to define | `POSIXLY_CORRECT'. | | Newer versions of POSIX are occasionally incompatible with older | versions. For example, older versions of POSIX required the command | `sort +1' to sort based on the second and succeeding fields in each | input line, but starting with POSIX 1003.1-2001 the same command is | required to sort the file named `+1', and you must instead use the | command `sort -k 2' to get the field-based sort. | | The GNU utilities normally conform to the version of POSIX that is | standard for your system. To cause them to conform to a different | version of POSIX, define the `_POSIX2_VERSION' environment variable to | a value of the form YYYYMM specifying the year and month the standard | was adopted. Two values are currently supported for `_POSIX2_VERSION': | `199209' stands for POSIX 1003.2-1992, and `200112' stands for POSIX | 1003.1-2001. For example, if you have a newer system but are running | software that assumes an older version of POSIX and uses `sort +1' or | `tail +10', you can work around any compatibility problems by setting | `_POSIX2_VERSION=199209' in your environment.
