Obsolete (The GNU Awk User’s Guide)
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2.9 Obsolete Options and/or Features
This section describes features and/or command-line options from previous releases of gawk that either are not available in the current version or are still supported but deprecated (meaning that they will not be in the next release).
The process-related special files /dev/pid, /dev/ppid, /dev/pgrpid, and /dev/user were deprecated in gawk 3.1, but still worked. As of version 4.0, they are no longer interpreted specially by gawk. (Use PROCINFO instead; see Built-in Variables That Convey Information.)
