2019年11月30日 · It's worth mentioning that the likely purpose of this code, especially when used with %s, is to print a sub-string of the original string. In this use case, str would point to somewhere inside the original string (possibly at the beginning), and str_len will specify the length of the sub-string that should be printed.

2021年3月2日 · (Compare printf '20%%\n' and printf '%s\n' '20%') It also makes the format easier to see for the reader, helping prevent the mistake of forgetting the trailing newline. Bottom line: it's a stylistic decision. There's no functional difference between: printf '%s\n' 'No input entered' and. printf 'No input entered\n'

2017年9月2日 · * Causes fprintf to pad the output until it is n characters wide, where n is an integer value stored in the a function argument just preceding that represented by the modified type. printf("%*d", 5, 10) //will result in "10" being printed with a width of 5.

It is not a modifier for %s format, as you seem to believe. This means that "%[^\n]s" format string will be interpreted by scanf as two independent format specifiers: %[^\n] followed by a lone s. This will direct scanf to read everything until \n is encountered (leaving \n unread), and then require that the next input character is s. This just ...

2022年11月11日 · Using %s in scanf without an explcit field width opens the same buffer overflow exploit that gets did; namely, if there are more characters in the input stream than the target buffer is sized to hold, scanf will happily write those extra characters to memory outside the buffer, potentially clobbering something important.

2015年2月12日 · sscanf(s, "%d %n", &i, &n) == 1 will be true. Therefore the other part of the && expression will execute. And s[n] will access some random place in memory because n is uninitialized. Interpreting the format: "%d %n" Attempts to scan a number which may be a decimal number or an integer or a scientific notation number.

2017年5月14日 · If you open the file in binary mode \n will give you a "unix style" line ending and "\r\n" will give you a "dos style" line ending. If you open the file in "text" mode on a dos/windows system then when you write \n the file handling code converts it to \r\n. So by opening a file in text mode and using \n you get the platform specific line ending.

name = 0xbff5391b &name[0] = 0xbff5391b name printed as %s is siva *name = s name[0] = s So 'name' is actually a pointer to the array of characters in memory. If you try reading the first four bytes at 0xbff5391b, you will see 's', 'i', 'v' and 'a'

2021年8月29日 · The %*s usage in the printf format string prints a %s specifier (in this case the empty string "") using a field width of n characters. An explanation of basic printf principles is basically outside the scope of this question (and answer); I'd recommend reading the printf documentation or asking your own separate question on SO.

2012年12月6日 · That is: \s matches a space( ) or a tab(\t) or a line(\n) break or a vertical tab(\x0B sometimes referred as \v) or a form feed(\f) or a carriage return(\r) . \\s*,\\s* It says zero or more occurrence of whitespace characters, followed by a comma and then followed by zero or more occurrence of whitespace characters.