3.2.165 sysopen

sysopen FILEHANDLE, FILENAME, MODE
sysopen FILEHANDLE, FILENAME, MODE, PERMS

This function opens the file whose filename is given by FILENAME, and associates it with FILEHANDLE. If FILEHANDLE is an expression, its value is used as the name of (or reference to) the filehandle. This function calls open(2) with the parameters FILENAME, MODE, PERMS.

The possible values and flag bits of the MODE parameter are system-dependent; they are available via the Fcntl library module. However, for historical reasons, some values are universal: zero means read-only, one means write-only, and two means read/write.

If the file named by FILENAME does not exist and sysopen creates it (typically because MODE includes the O_CREAT flag), then the value of PERMS specifies the permissions of the newly created file. If PERMS is omitted, the default value is 0666, which allows read and write for all. This default is reasonable: see umask.

The FileHandle module described in Chapter 7 provides a more object-oriented approach to sysopen. See also open earlier in this chapter.