MathViews Functions
Synopsis:
fclose(fHandle)
Description:
The fclose function closes the file(s) associated with fHandle.
Example:
|
A=1:10
fid = fopen('temp1.txt',
'w+')
nCnt = fwrite(fid,
A, 'ushort')
fseek(fid,0,'b')
[B, numpoints] = fread(fid,2,'ushort')
currentpos = ftell(fid)
C = fread(fid,2,'ushort')
currentpos =
ftell(fid)
fclose(fid) |
Related Topics:
File I/O functions
Synopsis:
feof(fHandle)
Description:
The feof function returns a nonzero value after the first read
operation that attempts to read past the end of the file associated with fHandle.
It returns 0 if the current position is not end of file. There is no error
return
The feof routine determines whether the end of file has been
reached. When end of file is reached, read operations return an end-of-file
indicator until the file is closed or until rewind, ftell, or fseek is called.
Example:
Related Topics:
File I/O functions
Synopsis:
ferror(fHandle)
Description:
The ferror tests for a reading or writing error on the file
associated with fHandle. If an error has occurred, the error indicator
for the file remains set until the file is closed or rewind is called.
Example:
Related Topics:
File I/O functions
Synopsis:
string = fgetl(fHandle)
Description:
The fgetl returns a string from the the file associated with fHandle.
It reads characters from the current file position to and including the first
newline character or to the end of the file whichever comes first. The newline
character, if read, is not included in the string (it is discarded).
Example:
Related Topics:
File I/O functions
Synopsis:
string = fgets(fHandle)
Description:
The fgets returns a string from the file associated with fHandle.
It reads characters from the current file position to and including the first
newline character or to the end of the file whichever comes first. The newline
character, if read, is included in the string.
Example:
Related Topics:
File I/O functions
Synopsis:
[fHandle, errmsg]=fopen(filename)
[fHandle, errmsg]=fopen(filename, mode)
fHandle=fopen('all')
Description:
The fopen function opens the file specified by filename and
returns a handle, fHandle, to the file. fHandle is an index to
an internally maintain array of open file handles. fHandle = -1 is an
invalid handle, the string errmsg provides more information regarding
the error.
fopen('all') returns the array of open file handles. You
can NOT open a filename 'all'.
The fHandle=fopen(filename, mode) function opens
the file specified by filename. The character string mode specifies the
type of access requested for the file, as follows:
- fopen modes
- 'r'
- Opens for reading. If the file does not exist or cannot be found, the fopen
call fails.
- 'w'
- Opens an empty file for writing. If the given file exists, its contents are
destroyed.
- 'a'
- Opens for writing at the end of the file (appending) without removing the
EOF marker before writing new data to the file; creates the file first if it
doesn't exist. This mode does not remove the EOF marker before appending to the
file. After appending has occurred, the MS-DOS TYPE command only shows data up
to the original EOF marker and not any data appended to the file.
- 'r+'
- Opens existing file for both reading and writing. (The file must exist).
- 'w+'
- Opens an empty file for both reading and writing. If the given file exists,
its contents are destroyed.
- 'a+'
- Opens for reading and appending; the appending operation includes the
removal of the EOF marker before new data is written to the file and the EOF
marker is restored after writing is complete; creates the file first if it
doesn't exist. The "a+" mode does remove the EOF marker before
appending to the file. After appending, the MS-DOS TYPE command shows all data
in the file. The "a+" mode is required for appending to a stream file
that is terminated with the CTRL+Z EOF marker.
When a file is opened with the "a" or "a+" access type,
all write operations occur at the end of the file. The file pointer can be
repositioned using fseek or rewind, but is always moved back to the end of the
file before any write operation is carried out. Thus, existing data cannot be
overwritten.
Example:
Related Topics:
File I/O functions
Synopsis:
byteCount=fprintf(fHandle, formatString, arg1,...)
Description:
The fprintf formats the data of arg1 (and any additional
variable listed after arg1) and writes a series of characters/values to
the file associated with fHandle. Each function argument (if any) is
converted and output according to the corresponding format specification in
format.
formatString specifications always begin with a percent sign (%) and
are read left to right. When printf encounters the first format specification
(if any), it converts the value of the first argument (if the argument is a
matrix, all the elements are converted) after format and outputs it accordingly.
The second format specification causes the second argument to be converted and
output, and so on. If there are more arguments than there are format
specifications, the extra arguments are ignored. Refer to your C language
reference manual for additional information regarding escape characters and
format specifications.
- Format specification
- consists of optional and required fields, has the following form:
%[flags] [width] [.precision]type
- Each field of the format specification is a single character or a number
signifying a particular format option. The simplest format specification
contains only the percent sign and a type character (for example, %s). If a
percent sign is followed by a character that has no meaning as a format field,
the character is copied to stdout. For example, to print a percent-sign
character, use %%. The optional fields, which appear before the type character,
control other aspects of the formatting
- type
-
- e
- Signed value having the form [ – ]d.dddd e [sign]ddd where d is a
single decimal digit, dddd is one or more decimal digits, ddd is exactly three
decimal digits, and sign is + or –.
- E
- Identical to the e format except that E rather than e introduces the
exponent.
- f
- Signed value having the form [ – ]dddd.dddd, where dddd is one or more
decimal digits. The number of digits before the decimal point depends on the
magnitude of the number, and the number of digits after the decimal point
depends on the requested precision.
- g
- Signed value printed in f or e format, whichever is more compact for the
given value and precision. The e format is used only when the exponent of the
value is less than –4 or greater than or equal to the precision argument.
Trailing zeros are truncated, and the decimal point appears only if one or more
digits follow it.
- G
- Identical to the g format, except that E, rather than e, introduces the
exponent (where appropriate).
- s
- Character string printed for the values of the argument. Matrix rows are
converted to a character string which are printed up to the first null character
(value 0) or until the precision value is reached.
- flags
- The first optional field of the format specification is flags. A flag
directive is a character that justifies output and prints signs, blanks, decimal
points, and octal and hexadecimal prefixes. More than one flag directive may
appear in a format specification.
- -
- Left align the result within the given field width
- +
- Prefix the output value with a sign (+ or –) if the output value is of
a signed type
- 0
- If width is prefixed with 0, zeros are added until the minimum width is
reached. If 0 and – appear, the 0 is ignored.
- #
- When used with the e, E, or f format, the # flag forces the output value to
contain a decimal point in all cases.
- When used with the g or G format, the # flag forces the output value to
contain a decimal point in all cases and prevents the truncation of trailing
zeros.
- width
- The second optional field of the format specification is the width
specification. The width argument is a nonnegative decimal integer controlling
the minimum number of characters printed. If the number of characters in
the output value is less than the specified width, blanks are added to the left
or the right of the values — depending on whether the – flag (for left
alignment) is specified — until the minimum width is reached. If width is
prefixed with 0, zeros are added until the minimum width is reached (not useful
for left-aligned numbers). The width specification never causes a value to be
truncated. If the number of characters in the output value is greater than the
specified width, or if width is not given, all characters of the value are
printed (subject to the precision specification).
- precision
- The third optional field of the format specification is the precision
specification. It specifies a nonnegative decimal integer, preceded by a period
(.), which specifies the number of characters to be printed, the number of
decimal places, or the number of significant digits (see below). Unlike the
width specification, the precision specification can cause either truncation of
the output value or rounding of a floating-point value.
- e, E
- The precision specifies the number of digits to be printed after the
decimal point. The last printed digit is rounded.
- f
- The precision value specifies the number of digits after the decimal point.
If a decimal point appears, at least one digit appears before it. The value is
rounded to the appropriate number of digits.
- g,G
- The precision specifies the maximum number of significant digits printed.
- s
- The precision specifies the maximum number of characters to be printed.
Characters in excess of precision are not printed.
Example:
Related Topics:
File I/O functions
Synopsis:
[var, numElements] =fread(fHandle, sizeSpec,
formatString)
var=fread(fHandle)
Description:
The fread function reads up to sizeSpec items of size
defined by the formatString from the input file associated with fHandle
and stores them in the output variable, var. The file pointer associated
with the file (if any) is increased by the number of bytes actually
read.
var=fread(fHandle) reads until end-of-file is
reached.
- sizeSpec
- sizeSpec is an [rows, cols] matrix specifying the shape of the
output data and the numebr of elements to read from the input file. If size is
not specified it defaults to inf, i.e. the file is scanned until EOF is
reached.
- formatString
- Control the number of bytes to read for each element of the output
variable.
- char
- Single byte
- schar, int8
- Single signed byte
- uchar, uint8
- Single unsigned byte
- short, int16
- Short signed integer (two bytes)
- ushort, uint16
- Short unsigned integer (two bytes)
- int, int32
- Signed 32-bit integer (four bytes)
- uint, uint32
- Unsigned 32-bit integer (four bytes)
- long
- Signed 32-bit integer (four bytes) - PC format
- ulong
- Unsigned 32-bit integer (four bytes) - PC format
- float, float32
- Single precision floating point number (four bytes)
- double, float64
- Double precision floating point number (eight bytes)
Example:
Related Topics:
File I/O functions
Synopsis:
[var, numElements] =fscanf(fHandle, formatString,
sizeSpec)
var=fscanf(fHandle, formatString)
Description:
The fscanf function reads up to sizeSpec items of format
defined by the formatString from the input file associated with fHandle
and stores them in the output variable, var. The file pointer associated
with the file (if any) is increased by the number of bytes actually
read.
var=fread(fHandle, formatString) reads until
end-of-file is reached.
- sizeSpec
- sizeSpec is an [rows, cols] matrix specifying the shape of the
output data and the numebr of elements to read from the input file. If size is
not specified it defaults to inf, i.e. the file is scanned until EOF is
reached.
formatString specifications, introduced by the percent sign (%). A
format specification causes scanf to read and convert characters in the input
into values of a specified type. The values are assigned to the elements of the
output argument, var.
- Format specification
- consists of optional and required fields, has the following form:
% [width]type
- The format is read from left to right. Characters outside format
specifications are expected to match the sequence of characters in the input
file; the matching characters in the file are scanned but not stored. If a
character in the file conflicts with the format specification, scanning
terminates, and the character is left in the file as if it had not been read.
- type
-
- c
- Single char
- d
- Decimal integer
- e, E, f, g, G
- Floating-point value consisting of optional sign (+ or –), series of
one or more decimal digits containing decimal point, and optional exponent ("e"
or "E") followed by an optionally signed integer value.
- s
- String, up to first white-space character (space, tab or newline).
- width
- Width is a positive decimal integer controlling the maximum number
of characters to be read from the file for each element. No more than width
characters are converted and stored at the corresponding argument element. Fewer
than width characters may be read if a white-space character (space, tab, or
newline) or a character that cannot be converted according to the given format
occurs before width is reached.
Example:
Related Topics:
File I/O functions
Synopsis:
fseek(fHandle, offset, originSpec)
Description:
The fseek function moves the file pointer (if any) associated with
with fHandle to a new location that is offset bytes from originSpec.
The next operation on the file takes place at the new location. On a file open
for update, the next operation can be either a read or a write.
originSpec are as follows:
- 'b'
- offset is specified from the beginning of file
- 'c'
- offset is specified from the current file pointer
position.
- 'e'
- offset is specified from the end of file
Example:
Related Topics:
File I/O functions
Synopsis:
ftell(fHandle)
Description:
The ftell returns the file pointer position (if any) associated
with with fHandle. On devices incapable of seeking (such as serail ports
and/or printers), or when fHandle does not refer to an open file, the
return value is -1.
Example:
Related Topics:
File I/O functions
Synopsis:
numElements=fwrite(fHandle, var, formatString)
Description:
The fwrite function writes all the elements of variable var
to the output file associated with fHandle using the format specified by
formatString. The file pointer associated with the file (if any) is
increased by the number of bytes actually written.
sizeSpec
formatString
Example:
Related Topics:
File I/O functions
Synopsis:
var=sprintf(formatString, arg1,...)
Description:
The sprintf formats the data of arg1 (and any additional
variable listed after arg1) and writes a series of characters/values to
the output variable, var. sprintf has the same functionality
of fprintf but rather than writing
to a file, the output is return via output variable.
Example:
Related Topics:
File I/O functions
Synopsis:
var=sscanf(inputString, formatString, sizeSpec)
var=sscanf(inputString, formatString)
Description:
The sscanf function reads up to sizeSpec items of format
defined by the formatString from the input string and stores them in the
output variable, var.sscanf has the same functionality of
fscanf but rather than reading from
a file, fscanf reads from inputString.
Example:
Related Topics:
File I/O functions
Synopsis:
_devctrl(fHandle, "Mode", modeSpec) - control
serial port mode setting
_devctrl(fHandle, "Timeout", timeoutSpec) -
control serial port timeout setting
Description:
The _devctrl(fHandle, "Mode", modeSpec) set the
mode for the serial port mode as specified by the modeSpec for the file
associated with fHandle.
- modeSpec
- [baud=b] [parity=p] [data=d] [stop=s] [to=on|off] [xon=on|off]
[odsr=on|off] [octs=on|off] [dtr=on|off|hs] [rts=on|off|hs|tg]
[idsr=on|off]
- baud=b
- Specifies the transmission rate in bits per second. The following list
shows valid abbreviations for b and its related rate:
11 110 baud
15 150 baud
30 300 baud
60 600 baud
12 1200 baud
24 2400 baud
48 4800 baud
96 9600 baud
19 19,200 baud
- parity=p
- Specifies how the system uses the parity bit to check for transmission
errors. The p value can be one of the following: n (none), e (even), o (odd), m
(mark), or s (space). The default value is e. Not all computers support the
values m and s.
- data=d
- Specifies the number of data bits in a character. Valid values for d are in
the range 5 through 8. The default value is 7. Not all computers support the
values 5 and 6.
- stop=s
- Specifies the number of stop bits that define the end of a character: 1,
1.5, or 2. If the baud rate is 110, the default value is 2; otherwise, the
default value is 1. Not all computers support the value 1.5.
- to=on|off
- Specifies whether infinite time-out processing is on or off. The default is
off.
- xon=on|off
- Specifies whether the xon or xoff protocol for data-flow control is on or
off.
- odsr=on|off
- Specifies whether output handshaking that uses the Data Set Ready (DSR)
circuit is on or off.
- octs=on|off
- Specifies whether output handshaking that uses the Clear To Send (CTS)
circuit is on or off.
- dtr=on|off
- Specifes whether the DTR circuit is on or off.
- rts=on|off|hs|tg
- Specifies whether the RTS circuit is set to on, off, handshake, or toggle.
- idsr=on|off
- Specifies whether the DSR circuit sensitivity is on or off.
The _devctrl(fHandle, "Timeout", timeoutSpec)
set the timeout for the serial port mode as specified by the timeoutSpec
for the file associated with fHandle.
- timeoutSpec
- Five element vector specifing the following values (in milliseconds):
[ReadIntervalTimeout, ReadTotalTimeoutMultiplier; ReadTotalTimeoutConstant;
WriteTotalTimeoutMultiplier; WriteTotalTimeoutConstant]. See Win32 documentation
on the COMMTIMEOUTS structure is used in the SetCommTimeouts() and
GetCommTimeouts() functions to set and query the time-out parameters for a
communications device.
Example: _devctrl(comm_fid, 'Mode', 'baud=9600')
_devctrl(comm_fid,
'Mode', 'baud=1200 parity=N data=8 stop=1')
_devctrl(comm_fid, 'Timeout',
[0, 0, 0, 0, 0])
Related Topics:
File I/O functions