For C/C++ programmers.
fscanf() does not work like C/C++, because PHP's fscanf() move file pointer the next line implicitly.
(PHP 4 >= 4.0.1, PHP 5, PHP 7)
fscanf — Parses input from a file according to a format
The function fscanf() is similar to
sscanf(), but it takes its input from a file
associated with handle
and interprets the
input according to the specified format
, which is
described in the documentation for sprintf().
Any whitespace in the format string matches any whitespace in the input stream. This means that even a tab \t in the format string can match a single space character in the input stream.
Each call to fscanf() reads one line from the file.
handle
A file system pointer resource that is typically created using fopen().
format
The format string is composed of zero or more directives: ordinary characters (excluding %) that are copied directly to the result and conversion specifications, each of which results in fetching its own parameter.
A conversion specification follows this prototype: %[flags][width][.precision]specifier.
Flag | Description |
---|---|
- | Left-justify within the given field width; Right justification is the default |
+ | Prefix positive numbers with a plus sign +; Default only negative are prefixed with a negative sign. |
(space) | Pads the result with spaces. This is the default. |
0 | Only left-pads numbers with zeros. With s specifiers this can also right-pad with zeros. |
'(char) | Pads the result with the character (char). |
An integer that says how many characters (minimum) this conversion should result in.
A period . followed by an integer who's meaning depends on the specifier:
Note: If the period is specified without an explicit value for precision, 0 is assumed.
Note: Attempting to use a position specifier greater than
PHP_INT_MAX
will generate warnings.
Specifier | Description |
---|---|
% | A literal percent character. No argument is required. |
b | The argument is treated as an integer and presented as a binary number. |
c | The argument is treated as an integer and presented as the character with that ASCII. |
d | The argument is treated as an integer and presented as a (signed) decimal number. |
e | The argument is treated as scientific notation (e.g. 1.2e+2). The precision specifier stands for the number of digits after the decimal point since PHP 5.2.1. In earlier versions, it was taken as number of significant digits (one less). |
E | Like the e specifier but uses uppercase letter (e.g. 1.2E+2). |
f | The argument is treated as a float and presented as a floating-point number (locale aware). |
F | The argument is treated as a float and presented as a floating-point number (non-locale aware). Available as of PHP 5.0.3. |
g |
General format. Let P equal the precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero. Then, if a conversion with style E would have an exponent of X: If P > X ⥠â4, the conversion is with style f and precision P â (X + 1). Otherwise, the conversion is with style e and precision P â 1. |
G | Like the g specifier but uses E and F. |
o | The argument is treated as an integer and presented as an octal number. |
s | The argument is treated and presented as a string. |
u | The argument is treated as an integer and presented as an unsigned decimal number. |
x | The argument is treated as an integer and presented as a hexadecimal number (with lowercase letters). |
X | The argument is treated as an integer and presented as a hexadecimal number (with uppercase letters). |
The c type specifier ignores padding and width
Attempting to use a combination of the string and width specifiers with character sets that require more than one byte per character may result in unexpected results
Variables will be co-erced to a suitable type for the specifier:
Type | Specifiers |
---|---|
string | s |
integer | d, u, c, o, x, X, b |
double | g, G, e, E, f, F |
...
The optional assigned values.
If only two parameters were passed to this function, the values parsed will be returned as an array. Otherwise, if optional parameters are passed, the function will return the number of assigned values. The optional parameters must be passed by reference.
Example #1 fscanf() Example
<?php
$handle = fopen("users.txt", "r");
while ($userinfo = fscanf($handle, "%s\t%s\t%s\n")) {
list ($name, $profession, $countrycode) = $userinfo;
//... do something with the values
}
fclose($handle);
?>
Example #2 Contents of users.txt
javier argonaut pe hiroshi sculptor jp robert slacker us luigi florist it
For C/C++ programmers.
fscanf() does not work like C/C++, because PHP's fscanf() move file pointer the next line implicitly.
It would be great to precise in the fscanf documentation
that one call to the function, reads a complete line.
and not just the number of values defined in the format.
If a text file contains 2 lines each containing 4 integer values,
reading the file with 8 fscanf($fd,"%d",$v) doesnt run !
You have to make 2
fscanf($fd,"%d %d %d %d",$v1,$v2,$v3,$v4);
Then 1 fscanf per line.
If you want to read text files in csv format or the like(no matter what character the fields are separated with), you should use fgetcsv() instead. When a text for a field is blank, fscanf() may skip it and fill it with the next text, whereas fgetcsv() correctly regards it as a blank field.
If you want to parse a cron file, you may use this pattern:
<?php
while ($cron = fscanf($fp, "%s %s %s %s %s %[^\n]s"))
{
}
?>
Yet another function to read a file and return a record/string by a delimiter. It is very much like fgets() with the delimiter being an additional parameter. Works great across multiple lines.
function fgetd(&$rFile, $sDelim, $iBuffer=1024) {
$sRecord = '';
while(!feof($rFile)) {
$iPos = strpos($sRecord, $sDelim);
if ($iPos === false) {
$sRecord .= fread($rFile, $iBuffer);
} else {
fseek($rFile, 0-strlen($sRecord)+$iPos+strlen($sDelim), SEEK_CUR);
return substr($sRecord, 0, $iPos);
}
}
return false;
}
actually, instead of trying to think of every character that might be in your file, excluding the delimiter would be much easier.
for example, if your delimiter was a comma use:
%[^,]
instead of:
%[a-zA-Z0-9.| ... ]
Just make sure to use %[^,\n] on your last entry so you don't include the newline.
to include all type of visible chars you should try:
<?php fscanf($file_handler,"%[ -~]"); ?>
fscanf works a little retardedly I've found. Instead of using just a plain %s you probably will need to use sets instead. Because it works so screwy compared to C/C++, fscanf does not have the ability to scan ahead in a string and pattern match correctly, so a seemingly perfect function call like:
fscanf($fh, "%s::%s");
With a file like:
user::password
Will not work. When fscanf looks for a string, it will look and stop at nothing except for a whitespace so :: and everything except whitespace is considered part of that string, however you can make it a little smarter by:
fscanf($fh, "%[a-zA-Z0-9,. ]::%[a-zA-Z0-9,. ]" $var1, $var2);
Which tells it that it can only accept a through z A through Z 0 through 9 a comma a period and a whitespace as input to the string, everything else cause it to stop taking in as input and continue parsing the line. This is very useful if you want to get a sentence into the string and you're not sure of exactly how many words to add, etc.
If you want fscanf()to scan one variable in a large number of lines, e.g an Ipadress in a line with more variables, then use fscanf with explode()
<?
$filename = "somefile.txt";
$fp = fopen($filename, "r") or die ("Error opening file! \n");
$u = explode(" ",$line); // $u is the variable eg. an IPadress
while ($line = fscanf($fp,"%s",$u)) {
if(preg_match("/^$u/",$_SERVER['REMOTE_ADDR'])) {$badipadresss++;} // do something and continue scan
}
?>
Besides, fscanf()is much faster than fgets()
The use of PHP code in the ACM submission
Here is a sample solution for problem 1001 using PHP:
<?php
while (fscanf(STDIN, "%d%d", $a, $b) == 2) {
print ($a + $b) . "\n";
}