mopen

open a file in Scilab

Calling Sequence

[fd, err] = mopen(file [, mode, swap ])

Arguments

:file a character string. The pathname of the file to open. : :mode a character string that controls whether the file is opened

for reading (r), writing (w), or appending (a) and whether the file is opened for updating (+). The mode can also include a b parameter to indicate a binary file. ‘rb’ default value

: :swap a scalar. If swap is present and swap = 0 then automatic

bytes swap is disabled. 1 default value

: :err a scalar. Error indicator. error value: error message: 0 No

error -1 no more logical units -2 cannot open file -3 no more memory -4 invalid name -5 invalid status

: :fd scalar. The fd parameter returned by the function mopen is

used as a file descriptor (it’s a positive integer).

:

Description

mopen may be used to open a file in a way compatible with the C fopen procedure. Without swap argument the file is supposed to be coded in “little endian IEEE format” and data are swaped if necessary to match the IEEE format of the processor.

The mode parameter controls the access allowed to the stream. The parameter can have one of the following values. In this list of values, the b character indicates a binary file

:r Opens the file for reading. : :rb Opens a binary file for reading. : :rt Opens a text file for reading. : :w Creates a new file for writing, or opens and truncates a file to

zero length.

: :wb Creates a new binary file for writing, or opens and truncates a

file to zero length.

: :wt Creates a text binary file for writing, or opens and truncates a

file to zero length.

: :a or ab Appends (opens a file for writing at the end of the file,

or creates a file for writing).

: :r+ or r+b Opens a file for update (reading and writing). : :w+ or w+b Truncates to zero length or creates a file for update. : :a+ or a+b Appends (opens a file for update, writing at the end of

the file, or creates a file for writing).

:

When you open a file for update, you can perform both input and output operations on the resulting stream. However, an output operation cannot be directly followed by an input operation without a file- positioning operation (mseek() function). Also, an input operation cannot be directly followed by an output operation without an intervening file positioning operation, unless the input operation encounters the end of the file.

When you open a file for append (that is, when the mode parameter is a or a+), it is impossible to overwrite information already in the file. You can use the fseek() function to reposition the file pointer to any position in the file, but when output is written to the file, the current file pointer is ignored. All output is written at the end of the file and the file pointer is repositioned to the end of the output.

To open files in a way compatible with Fortran like functions use function file.

// open a SCI+'/ACKNOWLEDGEMENTS' as text and read only
      fd_r = mopen(SCI+'/ACKNOWLEDGEMENTS', 'rt')

      // read five lines of fd_r
      `mgetl`_(fd_r, 5)

      // another way to read file
      // here read five words
      `mfscanf`_(5, fd_r, '%s')

      // close file descriptor associated to SCI+'/ACKNOWLEDGEMENTS' as text and read only
      `mclose`_(fd_r);

// open a file as text with write property
      fd_w = mopen(TMPDIR+'/write.txt', 'wt');

      // write a line in fd_w
      `mputl`_('This is a line of text', fd_w);
      `mclose`_(fd_w);

      // read text
      fd_r2 = mopen(TMPDIR+'/write.txt', 'rt');
      `mgetl`_(fd_r2)
      `mclose`_(fd_r2);

// read write a file as binary

      // first we write file
      fd_wb = mopen(TMPDIR+'/writeread.bin', 'wb')

      // put values as binary
      `mput`_(2003, 'l', fd_wb);
      `mput`_(2008, 'i', fd_wb);
      `mput`_(2012, 's', fd_wb);
      `mput`_(98, 'c', fd_wb);

      // close file descriptor associated to TMPDIR+'/writeread.bin'
      `mclose`_(fd_wb);

      // we read file
      fd_rb = mopen(TMPDIR+'/writeread.bin', 'rb')

      `mget`_(fd_rb, 'l')
      `mget`_(fd_rb, 'i')
      `mget`_(fd_rb, 's')
      `mget`_(fd_rb, 'c')

      `mclose`_(fd_rb)

See Also

• mclose closes an opened file
• merror tests the file access errors indicator
• meof check if end of file has been reached
• mfprintf converts, formats, and writes data to a file
• fprintfMat writes a matrix in a file
• mfscanf reads input from the stream pointer stream (interface to the C fscanf function)
• fscanfMat reads a matrix from a text file
• mget reads byte or word in a given binary format and converts to a double type
• mgetl reads lines from an text file
• mgetstr reads a character string from a file
• mprintf converts, formats, and writes data to the main scilab window
• mput writes byte or word in a given binary format
• mputl writes strings in an ascii file
• mputstr write a character string in a file
• mscanf
• mseek set current position in binary file.
• mtell binary file management
• mdelete deletes file(s)