( Conventions

Info Catalog ( POSIX ( Ports and File Descriptors
 38.1 POSIX Interface Conventions
 These interfaces provide access to operating system facilities.  They
 provide a simple wrapping around the underlying C interfaces to make
 usage from Scheme more convenient.  They are also used to implement the
 Guile port of  The Scheme shell (scsh).
    Generally there is a single procedure for each corresponding Unix
 facility.  There are some exceptions, such as procedures implemented for
 speed and convenience in Scheme with no primitive Unix equivalent,
 e.g., `copy-file'.
    The interfaces are intended as far as possible to be portable across
 different versions of Unix.  In some cases procedures which can't be
 implemented on particular systems may become no-ops, or perform limited
 actions.  In other cases they may throw errors.
    General naming conventions are as follows:
    * The Scheme name is often identical to the name of the underlying
      Unix facility.
    * Underscores in Unix procedure names are converted to hyphens.
    * Procedures which destructively modify Scheme data have exclamation
      marks appended, e.g., `recv!'.
    * Predicates (returning only `#t' or `#f') have question marks
      appended, e.g., `access?'.
    * Some names are changed to avoid conflict with dissimilar interfaces
      defined by scsh, e.g., `primitive-fork'.
    * Unix preprocessor names such as `EPERM' or `R_OK' are converted to
      Scheme variables of the same name (underscores are not replaced
      with hyphens).
    Unexpected conditions are generally handled by raising exceptions.
 There are a few procedures which return a special value if they don't
 succeed, e.g., `getenv' returns `#f' if it the requested string is not
 found in the environment.  These cases are noted in the documentation.
    For ways to deal with exceptions,  Exceptions.
    Errors which the C-library would report by returning a NULL pointer
 or through some other means are reported by raising a `system-error'
 exception.  The value of the Unix `errno' variable is available in the
 data passed by the exception.
    It can be extracted with the function `system-error-errno':
       (lambda ()
         (mkdir "/this-ought-to-fail-if-I'm-not-root"))
       (lambda stuff
         (let ((errno (system-error-errno stuff)))
            ((= errno EACCES)
             (display "You're not allowed to do that."))
            ((= errno EEXIST)
             (display "Already exists."))
             (display (strerror errno))))
Info Catalog ( POSIX ( Ports and File Descriptors
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