Perl: How to check if there is something being piped in

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LEARN ABOUT LINUX

checkbashisms

CHECKBASHISMS(1)                                              General Commands Manual                                             CHECKBASHISMS(1)

NAME

       checkbashisms - check for bashisms in /bin/sh scripts

SYNOPSIS

       checkbashisms script ...
       checkbashisms --help|--version

DESCRIPTION

       checkbashisms, based on one of the checks from the lintian system, performs basic checks on /bin/sh shell scripts for the possible presence
       of bashisms.  It takes the names of the shell scripts on the command line, and outputs warnings if possible bashisms are detected.

       Note that the definition of a bashism in this context roughly equates to "a shell feature that is not required to be supported  by  POSIX";
       this means that some issues flagged may be permitted under optional sections of POSIX, such as XSI or User Portability.

       In  cases  where  POSIX  and  Debian  Policy  disagree, checkbashisms by default allows extensions permitted by Policy but may also provide
       options for stricter checking.

OPTIONS

       --help, -h
              Show a summary of options.

       --newline, -n
              Check for "echo -n" usage (non POSIX but required by Debian Policy 10.4.)

       --posix, -p
              Check for issues which are non POSIX but required to be supported by Debian Policy 10.4 (implies -n).

       --force, -f
              Force each script to be checked, even if it would normally not be (for instance, it has a bash or non POSIX shell shebang or appears
              to be a shell wrapper).

       --extra, -x
              Highlight lines which, whilst they do not contain bashisms, may be useful in determining whether a particular issue is a false posi-
              tive which may be ignored.  For example, the use of "$BASH_ENV" may be preceded by checking whether "$BASH" is set.

       --version, -v
              Show version and copyright information.

EXIT VALUES

       The exit value will be 0 if no possible bashisms or other problems were detected.  Otherwise it will be the sum of the following error val-
       ues:

       1      A possible bashism was detected.

       2      A file was skipped for some reason, for example, because it was unreadable or not found.  The warning message will give details.

SEE ALSO

       lintian(1).

AUTHOR

       checkbashisms  was originally written as a shell script by Yann Dirson <dirson@debian.org> and rewritten in Perl with many more features by
       Julian Gilbey <jdg@debian.org>.

DEBIAN                                                           Debian Utilities                                                 CHECKBASHISMS(1)

Shell Programming and Scripting