Programming Perl, 4th Edition

sysopen

sysopen FILEHANDLE, FILENAME, MODE, MASK
sysopen FILEHANDLE, FILENAME, MODE

The sysopen 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. If FILEHANDLE is a variable whose value is undefined, a value will be created for you. The return value is true if the call succeeds, and false otherwise.

This function is a direct interface to your operating system’s open(2) syscall followed by an fdopen(3) library call. As such, you’ll need to pretend you’re a C programmer for a bit here. The possible values and flag bits of the MODE parameter are available through the Fcntl module. Because different systems support different flags, don’t count on all of them being available on your system. Consult your open(2) manpage or its local equivalent for details. Nevertheless, the flags listed in Table 27-7 should be present on any system with a reasonably standard C library.

Table 27-7. Flags for sysopen

Flag	Meaning
O_RDONLY	Read only.
O_WRONLY	Write only.
O_RDWR	Read and write.
O_CREAT	Create the file if it doesn’t exist.
O_EXCL	Fail if the file already exists.
O_APPEND	Append to the file.
O_TRUNC	Truncate the file.
O_NONBLOCK	Nonblocking access.

Many other options are ...