fopen
-- open a filefopen
(filename)
opens the file with the
name filename
.
fopen(filename)
fopen( <format,> filename, writemode)
filename |
- | the name of a file: a character string |
writemode |
- | either Write or Append. With both options, the file is opened for writing.
If no file by the name filename exists, a new file is
created. With Write, existing files are
overwritten. With Append, new data may be
appended to an existing file via the functions fprint or write . Note that in the Append mode, the specified format must coincide with the
format of the existing file; otherwise, the file cannot be opened and
fopen returns FAIL . |
format |
- | the write format: either Bin or Text. With Bin, the data are stored in MuPAD's binary format. With Text, standard ASCII format is used. The default is Bin. |
a positive integer: the file descriptor. FAIL
is returned if the file cannot be
opened.
The function is sensitive to the environment variable WRITEPATH
. If this variable has a
value, in write mode (using the options Write or
Append), the file is created in the corresponding
directory. Otherwise, the file is created in the ``working
directory''.
fclose
, finput
, fprint
, fread
, ftextinput
, pathname
, print
, protocol
, read
, READPATH
, write
, WRITEPATH
fopen
(filename)
opens an existing file
for reading. fopen
automatically identifies the file as a
text file or as a binary file. An error is raised if no file with the
specified name is found.fopen
( <format,> filename,
writemode)
opens the file for writing in the specified format.
If no file with the specified name exists, a new file is created.WRITEPATH
is considered. If
it has a value, a new file is created (or an existing file is searched
for) in the corresponding directory. Otherwise, it is created/searched
for in the ``working directory''.
Note that the ``working directory'' depends on the operating system. On Windows systems, it is the folder, where MuPAD is installed. On UNIX or Linux systems, the ``working directory'' is the directory where MuPAD was started.
In read mode, fopen
does not search for files in the
directories given by READPATH
and LIBPATH
.
On the Macintosh, an empty file name may be given. In this case, a dialog box is opened in which the user can choose a file. Further, on the interactive level, MacMuPAD warns the user if an existing file is about to be overwritten.
Also absolute path names are processed by fopen
.
fopen
can be used by
various functions such as fclose
, fread
, fprint
, read
, write
etc.fopen
should be closed by fclose
after use.fopen
is a function of the system kernel.We open the file test
for writing. With the
option Write
, it is not necessary
that the file test
exists. By default, the file is opened
as a binary file:
>> n := fopen("test", Write)
17
We write a string to the file and close it:
>> fprint(n, "a string"): fclose(n):
We append another string to the file:
>> n := fopen("test", Append)
18
>> fprint(n, "another string"): fclose(n):
The binary file cannot be opened as a text file for appending data:
>> n := fopen(Text, "test", Append)
FAIL
However, it may be opened as a text file with the option
Write
. The existing binary file is
overwritten as a text file:
>> n := fopen(Text, "test", Write)
19
>> fclose(n): delete n:
fopen
fails to open non-existing files for
reading. Here we assume that the file xyz
does not
exist:
>> n := fopen("xyz")
FAIL
We assume that the file test
created in
example 1 exists. It can be opened for
reading successfully:
>> n := fopen("test")
20
>> fclose(n): delete n: