S9 EXT  (sys:catch-errors boolean)  ==>  unspecific

When a SYS-UNIX extension procedure called by an S9 program fails,
the interpreter will normally generate an error condition and
abort program execution. When #T is passed to SYS:CATCH-ERRORS,
though, procedures will return #F instead of aborting program
execution and procedures that normally succeed silently will
return #T in case of success. E.g.:

    (sys:rmdir "non-existent-directory")  ==>  undefined
    (sys:strerror (sys:errno))            ==>  "No such file or directory"
    (sys:catch-errors #t)
    (sys:errno)                           ==>  0
    (sys:rmdir "non-existent-directory")  ==>  #f
    (sys:strerror (sys:errno))            ==>  "No such file or directory"

SYS:CATCH-ERRORS will also reset SYS:ERRNO when applied to #T.

(sys:catch-errors #t)  ==>  unspecific
