LIBSTDBUF(3)           FreeBSD Library Functions Manual           LIBSTDBUF(3)

NAME
     libstdbuf - preloaded library to change standard streams initial
     buffering

DESCRIPTION
     The libstdbuf library is meant to be preloaded with the LD_PRELOAD
     environment variable to as to change the initial buffering of standard
     input, standard output and standard error streams.

     Although you may load and configure this library manually, an utility,
     stdbuf(1), can be used to run a command with the appropriate environment
     variables.

ENVIRONMENT
     Each stream can be configured independently through the following
     environment variables (values are defined below):

           _STDBUF_I
                 Initial buffering definition for the standard input stream

           _STDBUF_O
                 Initial buffering definition for the standard output stream

           _STDBUF_E
                 Initial buffering definition for the standard error stream

     Each variable may take one of the following values:

           "0"   unbuffered

           "L"   line buffered

           "B"   fully buffered with the default buffer size

           size  fully buffered with a buffer of size bytes (suffixes 'k', 'M'
                 and 'G' are accepted)

EXAMPLE
     In the following example, the stdout stream of the awk(1) command will be
     fully buffered by default because it does not refer to a terminal.
     libstdbuf is used to force it to be line-buffered so vmstat(8)'s output
     will not stall until the full buffer fills.

           # vmstat 1 | LD_PRELOAD=/usr/lib/libstdbuf.so \
               STDBUF_1=L awk '$2 > 1 || $3 > 1' | cat -n

     See also the manpage of stdbuf(1) for a simpler way to do this.

HISTORY
     The libstdbuf library first appeared in FreeBSD 8.4.

AUTHORS
     The original idea of the libstdbuf command comes from Padraig Brady who
     implemented it in the GNU coreutils.  Jeremie Le Hen implemented it on
     FreeBSD.

FreeBSD 13.1-RELEASE-p6         April 28, 2012         FreeBSD 13.1-RELEASE-p6