rdchk(S)                       6 January 1993                       rdchk(S)


 Name

    rdchk - checks to see if there is data to be read

 Syntax


    cc ... -lx


    int rdchk(fdes)
    int fdes;


 Description

    rdchk checks to see if a process will block if it attempts to read the
    file designated by fdes.  rdchk returns 1 if the process will not block
    when a read is attempted or if it is the end of the file (EOF).  In this
    context, the proper sequence of calls using rdchk is:

       if(rdchk(fildes) > 0)

       read(fildes, buffer, nbytes);


 Diagnostics

    rdchk returns -1 if an error occurs (for example, EBADF), 0 when the pro-
    cess will block if it issues a read and 1 if it is okay to read.  EBADF
    is returned if a rdchk is used on a semaphore file or if the file speci-
    fied does not exist.

 See also

    read(S)

 Standards conformance

    rdchk is not part of any currently supported standard; it is an extension
    of AT&T System V provided by the Santa Cruz Operation.