c/cpp IO

c中读取输出

1. 单个字符 int fgetc( FILE *stream ); int fputc( int ch, FILE *stream );

   int ungetc( int ch, FILE *stream );

   ​int scanf( const char* format, ... ) int fscanf( std::FILE* stream, const char* format, ... ) int sscanf( const char* buffer, const char* format, ... ) 返回读取的参数的数量， or EOF The conversion specifiers that do not consume leading whitespace: %c、%[、%n

2. 一串字符 char *fgets( char *restrict str, int count, FILE *restrict stream ); 读取count-1个字符(一个用于存储'\0'__ null-terminated), parse stop when end-of-file or a newline found; it contain the newline character if success: return str; if error: return NULL

   int fputs( const char *restrict str, FILE *restrict stream );

3. unix最大打开文件数 #define FOPEN_MAX 20 /* must be <= OPEN_MAX <sys/syslimits.h> */

c++中读取输出

1. 一串字符 std::basic_istream<CharT,Traits>& std::getline(std::basic_istream<CharT,Traits>& input, std::basic_string<CharT,Traits,Allocator>& str, CharT delim ) 读取字符存到str, parse stop when end-of-file or delim found; extract the delim character, but not contain the delim character

2. 单个字符 char c; cin >> c cin.ignore(ignore_num, delim) Extracts and discards characters from the input stream until and including delim

3. cin mixed with getline >> input: 2 request=10 release=20

when used cin >> n, then getline(cin, str), because of getline will not consume the delimter left by cin

cin >> n
- cin >> std::ws //removing left whitespace
- cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n') //ingore all left over characters on the line
- getline(cin, notusestr); // explicit remove the newline charactor