Main Content


File I/O error information



message = ferror(fileID) returns the error message for the most recent file I/O operation on the specified file.

[message,errnum] = ferror(fileID) returns the error number that is associated with the error message.

[message,errnum] = ferror(fileID,'clear') clears the error indicator for the specified file. Specify the literal clear as a character vector or a string scalar. When you clear the error indicator, succeeding calls to ferror behave as if the most recent I/O operation is successful.


collapse all

Return the details for the most recent file I/O error on a file that you specify.

Open the file to read.

fid = fopen('outages.csv','r');

Set the read position to -5 bytes from the beginning of the file. Since no data exists before the beginning of the file, fseek returns -1 indicating that the operation was unsuccessful.

status = fseek(fid,-5,'bof')
status = -1

Get the details on the most recent error message on the file using its file identifier fid.

error = ferror(fid) 
error = 
'Offset is bad - before beginning-of-file.'

Close the file.


Input Arguments

collapse all

File identifier of an open file, specified as an integer. fileID can be one of these values:

  • N — Input or output from a file with a valid file identifier generated by the fopen function. N is equal to or greater than 3.

  • 0 — Input from a standard input device.

  • 1 — Output to a standard output device.

  • 2 — Standard error.

Data Types: double

Output Arguments

collapse all

Error message, returned as character vector containing the error message associated with the most recent I/O operation. If the most recent I/O operation is successful or if you clear it manually, then message is an empty character vector.

Error number, returned as an integer code associated with the error from most recent file I/O operation. If the most recent file I/O operation is successful, then errnum is 0. A nonzero errnum indicates an error:

  • Negative values correspond to MATLAB® error messages.

  • Positive values correspond to C library error messages for your system.

Extended Capabilities

Version History

Introduced before R2006a

expand all