fputs

Purpose

Writes strings to a file.

Format

numl = fputs(f, sa)
Parameters:
  • f (scalar) – file handle of a file opened with fopen().
  • sa (string or string array) – data
Returns:

numl (scalar) – the number of lines written to the file.

Examples

Write string to text file

// Create string
quote = "There is nothing either good or bad, but thinking makes it so.";

// Open file for writing
fh = fopen("hamlet.txt", "w");

// Write the string to the first line of the file
call fputs(fh, quote);

// Close the file
call close(fh);

After the code above, you should have a file named hamlet.txt in your current working directory, containing the contents of the quote string.

Write CSV data to text file

/*
** Create string containing a comma separated list
** of variable names and an ending newline
*/
text = "alpha,beta,gamma,delta\n";

fh = fopen("temp.csv", "w");

// Write the string to the first line of the file
call fputs(fh, text);

// Create some numeric data
x = { 1 2 3 4,
      5 6 7 8 };

// Convert numeric data to 2x4 string array
x_str = ntos(x);

/*
** Combine each row of 'x_str' into
** a single comma separated string
*/
x_str = strjoin(x_str, ",");

// Add newlines to the end of each line
x_str = x_str $+ "\n";

// Write the comma separated data to the file
call fputs(fh, x_str);

// Close the file
call close(fh);

After the above code, you should have a file named temp.csv with the following contents:

alpha,beta,gamma,delta
1,2,3,4
5,6,7,8

Note that saved() provides a simpler way to write CSV data.

Remarks

  • To write to the standard output stream or the standard error stream, pass in __STDOUT or __STDERR as the file handle argument.

    str = "sample string";
    num = fputs(__STDOUT, str);
    
  • fputs() writes the contents of each string in sa, minus the null terminating byte, to the file specified. If the file was opened in text mode (see fopen()), any newlines present in the strings are converted to carriage return-linefeed sequences on output.

  • If numl is not equal to the number of elements in sa, there may have been an I/O error while writing the file. You can use fcheckerr() or fclearerr() to check this. If there was an error, you can call fstrerror() to find out what it was.

  • If the file was opened for update (see fopen()) and you are switching from reading to writing, don’t forget to call fseek() or fflush() first, to flush the file’s buffer.

  • If you pass fputs() the handle of a file opened with open (i.e., a dataset or matrix file), your program will terminate with a fatal error.

Portability

Linux/macOS

Carriage return-linefeed conversion for files opened in text mode is unnecessary, because in Linux/macOS a newline is simply a linefeed.

See also

Functions fputst(), fopen()