Lua4z
A binary distribution of Lua for z/OS, with batteries

Module io

I/O standard library for manipulating files.

Functions

bpxwdyn (s) Calls the BPXWDYN service, a text interface to dynamic allocation and dynamic output.
close (file) Equivalent to file:close().
flush () Equivalent to file:flush over the default output file.
input (file) When called with a file name, it opens the named file (in text mode), and sets its handle as the default input file.
lines (filename) Opens the given file name in read mode and returns an iterator function that, each time it is called, returns a new line from the file.
open (filename, mode) Opens a file in the mode specified in the string mode.
output (file) Similar to io.input, but operates over the default output file.
popen (prog, mode) Starts program prog in a separated process and returns a file handle that you can use to read data from this program (if mode is "r", the default) or to write data to this program (if mode is "w").
read (...) Equivalent to io.input():read.
tmpfile () Returns a handle for a temporary file.
type (obj) Checks whether obj is a valid file handle.
write (...) Equivalent to io.output():write.
file:blksize () Gets the block size of the file.
file:close () Closes file.
file:delrec () Deletes a record from a VSAM file.
file:flush () Saves any written data to file.
file:lines () Returns an iterator function that, each time it is called, returns a new line from the file.
file:locate (key) Locates a VSAM record.
file:lrecl () Gets the logical record length (LRECL) of the file.
file:recfm () Gets the record format (RECFM) of the file.
file:openmode () Returns the mode that the file was opened with: "binary", "record", or "text".
file:read (...) Reads the file file, according to the given formats, which specify what to read.
file:rewind () Set the file position to the beginning of the file.
file:seek (whence, offset) Sets and gets the file position, measured from the beginning of the file, to the position given by offset plus a base specified by the string whence, as follows: "set": base is position 0 (beginning of the file); "cur": base is current position; "end": base is end of file; In case of success, function seek returns the final file position, measured in bytes from the beginning of the file.
file:setvbuf (mode, size) Sets the buffering mode for an output file.
file:update (buf) Updates a VSAM record.
file:vsamRBA () Gets the relative byte address (RBA) of the last VSAM record inserted or updated.
file:vsamtype () Gets the VSAM type.
file:write (...) Writes the value of each of its arguments to the file.

Fields

LOCATE_KEY_FIRST
LOCATE_KEY_LAST
LOCATE_KEY_EQ
LOCATE_KEY_EQ_BWD

Functions

bpxwdyn (s)
Calls the BPXWDYN service, a text interface to dynamic allocation and dynamic output.

For details, see the IBM documentation for bpxwdyn.

Parameters:

  • s string The BPXWDYN parameter string.
close (file)
Equivalent to file:close(). Without a file, closes the default output file.

Parameters:

  • file
flush ()
Equivalent to file:flush over the default output file.
input (file)
When called with a file name, it opens the named file (in text mode), and sets its handle as the default input file. When called with a file handle, it simply sets this file handle as the default input file. When called without parameters, it returns the current default input file. In case of errors this function raises the error, instead of returning an error code.

Parameters:

  • file
lines (filename)
Opens the given file name in read mode and returns an iterator function that, each time it is called, returns a new line from the file. Therefore, the construction

for line in io.lines(filename) do *body* end

will iterate over all lines of the file. When the iterator function detects the end of file, it returns nil (to finish the loop) and automatically closes the file.

The call io.lines() (with no file name) is equivalent to io.input():lines(); that is, it iterates over the lines of the default input file. In this case it does not close the file when the loop ends.

Parameters:

  • filename
open (filename, mode)
Opens a file in the mode specified in the string mode. It returns a new file handle, or, in case of errors, nil plus an error message.

This function calls the fopen() z/OS C runtime library function.

Parameters:

Returns:

    A file handle.

Usage:

     -- Open a sequential binary data set for reading
     local file = io.open("//'PAY.SEQ'", "rb, type=record, noseek")
    
     -- Open a PDS member for reading text
     local file = io.open("//PDS(MEMBER)", "rt, type=record")
    
     -- Open a z/OS UNIX file for writing
     local file = io.open("/u/lua/readme.md", "w")
output (file)
Similar to io.input, but operates over the default output file.

Parameters:

  • file
popen (prog, mode)
Starts program prog in a separated process and returns a file handle that you can use to read data from this program (if mode is "r", the default) or to write data to this program (if mode is "w"). This function is system dependent and is not available on all platforms.

Parameters:

  • prog
  • mode
read (...)
Equivalent to io.input():read.

Parameters:

  • ...
tmpfile ()
Returns a handle for a temporary file. This file is opened in update mode and it is automatically removed when the program ends.
type (obj)
Checks whether obj is a valid file handle. Returns the string "file" if obj is an open file handle, "closed file" if obj is a closed file handle, or nil if obj is not a file handle.

Parameters:

  • obj
write (...)
Equivalent to io.output():write.

Parameters:

  • ...
file:blksize ()
Gets the block size of the file.

Returns:

    An integer that represent the block size of the file in bytes.
file:close ()
Closes file. Note that files are automatically closed when their handles are garbage collected, but that takes an unpredictable amount of time to happen.
file:delrec ()
Deletes a record from a VSAM file.

The file must have been previously read by the read function to set the position.

This function calls the fdelrec() z/OS C runtime library function.

Returns:

    true if the delete was successful, otherwise false.
file:flush ()
Saves any written data to file.
file:lines ()
Returns an iterator function that, each time it is called, returns a new line from the file. Therefore, the construction for line in file:lines() do body end will iterate over all lines of the file. (Unlike io.lines, this function does not close the file when the loop ends.)
file:locate (key)
Locates a VSAM record.

This function calls the flocate() z/OS C runtime library function.

Parameters:

  • key The key used for positioning. If key is a number it is either a VSAM record number (for RRDS) or an RBA. Otherwise, key is a character string.

Returns:

    true if the locate was successful, otherwise false.
file:lrecl ()
Gets the logical record length (LRECL) of the file.

Returns:

    An integer that represents the LRECL of the file in bytes.
file:recfm ()
Gets the record format (RECFM) of the file.

Returns:

    A string. For example, "FB" for a fixed-blocked data set.
file:openmode ()
Returns the mode that the file was opened with: "binary", "record", or "text".
file:read (...)

Reads the file file, according to the given formats, which specify what to read. For each format, the function returns a string (or a number) with the characters read, or nil if it cannot read data with the specified format. When called without formats, it uses a default format that reads the entire next line (see below).

The available formats are:

  • "*n": reads a number; this is the only format that returns a number instead of a string.
  • "*a": reads the whole file, starting at the current position. On end of file, it returns the empty string.
  • "*l": reads the next line (skipping the end of line), returning nil on end of file. This is the default format when the file is opened in text mode.
  • "*r": reads the next record, returning nil on end of file. This is the default format when the file is opened in record mode.
  • *number*: reads a string with up to this number of characters, returning nil on end of file. If number is zero, it reads nothing and returns an empty string, or nil on end of file.

Parameters:

  • ...
file:rewind ()
Set the file position to the beginning of the file.
file:seek (whence, offset)
Sets and gets the file position, measured from the beginning of the file, to the position given by offset plus a base specified by the string whence, as follows: "set": base is position 0 (beginning of the file); "cur": base is current position; "end": base is end of file; In case of success, function seek returns the final file position, measured in bytes from the beginning of the file. If this function fails, it returns nil, plus a string describing the error. The default value for whence is "cur", and for offset is 0. Therefore, the call file:seek() returns the current file position, without changing it; the call file:seek("set") sets the position to the beginning of the file (and returns 0); and the call file:seek("end") sets the position to the end of the file, and returns its size.

Parameters:

  • whence
  • offset
file:setvbuf (mode, size)

Sets the buffering mode for an output file. There are three available modes:

  • "no": no buffering; the result of any output operation appears immediately.
  • "full": full buffering; output operation is performed only when the buffer is full (or when you explicitly flush the file (see io.flush)).
  • "line": line buffering; output is buffered until a newline is output or there is any input from some special files (such as a terminal device). For the last two cases, size specifies the size of the buffer, in bytes. The default is an appropriate size.

Parameters:

  • mode
  • size
file:update (buf)
Updates a VSAM record.

This function calls the fupdate() z/OS C runtime library function.

Parameters:

  • buf string The string to update the current record with.

Returns:

    An integer that represents the size of the updated record in bytes.
file:vsamRBA ()
Gets the relative byte address (RBA) of the last VSAM record inserted or updated.

Undefined for non-VSAM files.

Returns:

    A 4-byte integer from the C library amrc.RBA field.
file:vsamtype ()
Gets the VSAM type.
file:write (...)
Writes the value of each of its arguments to the file. The arguments must be strings or numbers. To write other values, use tostring or string.format before write.

Parameters:

  • ...

Fields

LOCATE_KEY_FIRST
  • LOCATE_KEY_FIRST locate() constant value
LOCATE_KEY_LAST
  • LOCATE_KEY_LAST locate() constant value
LOCATE_KEY_EQ
  • LOCATE_KEY_EQ locate() constant value
LOCATE_KEY_EQ_BWD
  • LOCATE_KEY_EQ_BWD locate() constant value