std::fgets - cppreference.com (original) (raw)
Reads at most count - 1 characters from the given file stream and stores them in the character array pointed to by str. Parsing stops if a newline character is found, in which case str will contain that newline character, or if end-of-file occurs. If bytes are read and no errors occur, writes a null character at the position immediately after the last character written to str.
[edit] Parameters
| str | - | pointer to an element of a char array |
|---|---|---|
| count | - | maximum number of characters to write (typically the length of str) |
| stream | - | file stream to read the data from |
[edit] Return value
str on success, null pointer on failure.
If the end-of-file condition is encountered, sets the eof indicator on stream (see std::feof()). This is only a failure if it causes no bytes to be read, in which case a null pointer is returned and the contents of the array pointed to by str are not altered (i.e. the first byte is not overwritten with a null character).
If the failure has been caused by some other error, sets the error indicator (see std::ferror()) on stream. The contents of the array pointed to by str are indeterminate (it may not even be null-terminated).
[edit] Notes
POSIX additionally requires that fgets sets errno if it encounters a failure other than the end-of-file condition.
Although the standard specification is unclear in the cases where count <= 1, common implementations do
if count < 1, do nothing, report error,
if count == 1,
some implementations do nothing, report error,
others read nothing, store zero in str[0], report success.
[edit] Example
Output:
Alan Tu. 41 6C 61 6E 20 54 75 00 ring..u. 72 69 6E 67 0A 00 75 00 John vo. 4A 6F 68 6E 20 76 6F 00 n Neuma. 6E 20 4E 65 75 6D 61 00 nn..uma. 6E 6E 0A 00 75 6D 61 00 Alonzo . 41 6C 6F 6E 7A 6F 20 00 Church.. 43 68 75 72 63 68 0A 00