Input / Output

OADL has a full-featured file input/output feature set. It supports both text-mode and binary-mode I/O, and supports pipes as well if the host operating system supports them. A full set of support routines for handing file positioning and errors is implemented.

Files

The base for OADL I/O is the File, which is an OADL handle to either a file that resides in the host operating system's file system, or a pipe to an external program. OADL defines three Files for program use:

io::Input

The standard input File. It might refer to the input console, or it might refer to a file or pipe if the host operating system supports redirection

io::Output

The standard output File. It might refer to the output console, or it might refer to a file or pipe if the host operating system supports redirection

io::ErrOut

The standard error output File. Again, its actual destination depends on operating system support.

Other files are associated with external file system or program resources via the new syntax:

where name is the name of the external file or external program, and mode is the file mode.

Various queries and state management methods are provided for File handles:

file.binary()

Query whether file was opened in binary mode

file.clearerr()

Clears any error conditions found on file

file.close()

file.close(disp)

Close the given file. It is an error to access it after it is closed.

file.feof()

Query whether file is at the end-of-file

file.ferror()

Returns the operating system error status associated with file

file.fflush()

Flush any pending buffered output to file

file.fseek(offs, whence)

Change the read/write position of file

file.ftell()

Query the read/write position of file

file.getswab()

Query whether file is in automatic byte-swap mode

file.ispipe()

Query whether file was opened as a pipe

file.readonly()

Query whether file was opened read-only

file.rewind()

Reset the read/write position of file to the beginning-of-file

file.setswab(bSwab)

Sets the automatic byte-swap mode of file.

Formatted Input / Output

OADL supports the formatting and printing of values to ouput files, and the reading of formatted values from input files. The files must be text-mode; the input/output strings are translated from or to streams of UTF-8 sequences. The following intrinsic procedures and method perform formatted input and output:

print(fmtstring, arg, ...)

print(file, fmtstring, arg, ...)

file.print(fmtstring, arg, ...)

Format and print several values

read(fmtstring, typ, ...)

read(file, fmtstring, typ, ...)

file.read(fmtstring, typ, ...)

Read a formatted set of values of the specified types from a file

say(val,val,...)

say(file,val,val,...)

file.say(val val,...)

Print out values to a file using a default format.

Streaming Input / Output

These intrinsic procedures and methods operate character-at-a-time on the input / output files. They support both text-mode and binary-mode files. If used with unformatted files, they operate byte-at-a-time, which can lead to unexpected effects with WideChar values.

getchar()

getchar(file)

file.getchar()

Get a single character of input from a file

putchar(ch)

putchar(file, ch)

file.putchar(ch)

Put a single character to a file

ungetc(ch)

ungetc(file, ch)

file.ungetc(ch)

Return a single character to the file input buffer

readstr()

readstr(file)

file.readstr()

Read a single line of input into a string

OADL supports unformatted reading and writing of values to files. These files must be opened in binary-mode. The values may be byte-swapped on read and write; see setswab and getswab for more information.

read(file, typ, typ, ...)

file.read(typ, typ, ...)

Read binary values from a file

write(file, val, val, ...)

file.write(val, val, ...)

Write binary values to a file

Back to External Procedures

Continue to OADL Format Specifiers

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