Capture characters from standard input without waiting for enter to be pressed

Question

I can never remember how I do this because it comes up so infrequently for me  But in C or C    what is the best way to read a character from standard input without waiting for a newline  press enter    Also ideally it wouldn t echo the input character to the screen  I just want to capture keystrokes with out effecting the console screen

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If you are on windows  you can use PeekConsoleInput to detect if there s any input    HANDLE handle   GetStdHandle STD INPUT HANDLE   DWORD events  INPUT RECORD buffer  PeekConsoleInput  handle   amp buffer  1   amp events      then use ReadConsoleInput to  consume  the input character     PeekConsoleInput handle   amp buffer  1   amp events   if events  gt  0        ReadConsoleInput handle   amp buffer  1   amp events         return buffer Event KeyEvent wVirtualKeyCode    else return 0   to be honest this is from some old code I have  so you have to fiddle a bit with it   The cool thing though is that it reads input without prompting for anything  so the characters are not displayed at all

User · Answer

C and C   take a very abstract view of I O  and there is no standard way of doing what you want   There are standard ways to get characters from the standard input stream  if there are any to get  and nothing else is defined by either language   Any answer will therefore have to be platform-specific  perhaps depending not only on the operating system but also the software framework   There s some reasonable guesses here  but there s no way to answer your question without knowing what your target environment is

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The following is a solution extracted from Expert C Programming  Deep Secrets  which is supposed to work on SVr4  It uses stty and ioctl      include  lt sys filio h gt  int kbhit      int i   ioctl 0  FIONREAD   amp i    return i     return a count of chars available to read      main      int i   0   intc      system  stty raw -echo     printf  enter  q  to quit  n     for   c   q  i          if  kbhit              c getchar           printf   n got  c  on iteration  d  c  i            system  stty cooked echo

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Assuming Windows  take a look at the ReadConsoleInput function

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Assuming Windows  take a look at the ReadConsoleInput function

User · Answer

Here s a version that doesn t shell out to the system  written and tested on macOS 10 14    include  lt unistd h gt   include  lt termios h gt   include  lt stdio h gt   include  lt string h gt   char  getStr  char  buffer   int maxRead       int  numRead    0    char ch     struct termios old    0     struct termios new    0     if  tcgetattr  0    amp old    lt  0          perror   tcgetattr   old settings       if  tcgetattr  0    amp new    lt  0          perror   tcgetaart   new settings       cfmakeraw   amp new      if  tcsetattr  0   TCSADRAIN    amp new    lt  0   perror   tcssetattr makeraw new        for  int i   0   i  lt  maxRead   i           ch   getchar        switch  ch            case EOF         case   n         case   r           goto exit getStr          break         default          printf    1c    ch            buffer  numRead       ch          if  numRead  gt   maxRead                goto exit getStr                    break             exit getStr    if  tcsetattr  0   TCSADRAIN    amp old   lt  0    perror   tcsetattr reset to old       printf    n          return buffer      int main  void        const int maxChars   20    char      stringBuffer  maxChars 1      memset    stringBuffer   0   maxChars 1       initialize to 0    printf   enter a string        getStr  stringBuffer   maxChars      printf   you entered    s  n    stringBuffer

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I use kbhit   to see if a char is present and then getchar   to read the data   On windows  you can use  conio h   On linux  you will have to implement your own kbhit     See code below      kbhit  include  lt stdio h gt   include  lt sys ioctl h gt     For FIONREAD  include  lt termios h gt   include  lt stdbool h gt   int kbhit void        static bool initflag   false      static const int STDIN   0       if   initflag               Use termios to turn off line buffering         struct termios term          tcgetattr STDIN   amp term           term c lflag  amp    ICANON          tcsetattr STDIN  TCSANOW   amp term           setbuf stdin  NULL           initflag   true             int nbbytes      ioctl STDIN  FIONREAD   amp nbbytes       0 is STDIN     return nbbytes        main  include  lt unistd h gt   int main int argc  char   argv        char c        setbuf stdout  NULL      Optional  No buffering        setbuf stdin  NULL       Optional  No buffering      printf  Press key        while   kbhit              printf               fflush stdout           sleep 1             c   getchar        printf   nChar received  c n   c       printf  Done  n         return 0

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That s not possible in a portable manner in pure C    because it depends too much on the terminal used that may be connected with stdin  they are usually line buffered   You can  however use a library for that    conio available with Windows compilers  Use the  getch   function to give you a character without waiting for the Enter key  I m not a frequent Windows developer  but I ve seen my classmates just include  lt conio h gt  and use it  See conio h at Wikipedia  It lists getch    which is declared deprecated in Visual C     curses available for Linux  Compatible curses implementations are available for Windows too  It has also a getch   function   try man getch to view its manpage   See Curses at Wikipedia     I would recommend you to use curses if you aim for cross platform compatibility  That said  I m sure there are functions that you can use to switch off line buffering  I believe that s called  raw mode   as opposed to  cooked mode  - look into man stty   Curses would handle that for you in a portable manner  if I m not mistaken

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If you are on windows  you can use PeekConsoleInput to detect if there s any input    HANDLE handle   GetStdHandle STD INPUT HANDLE   DWORD events  INPUT RECORD buffer  PeekConsoleInput  handle   amp buffer  1   amp events      then use ReadConsoleInput to  consume  the input character     PeekConsoleInput handle   amp buffer  1   amp events   if events  gt  0        ReadConsoleInput handle   amp buffer  1   amp events         return buffer Event KeyEvent wVirtualKeyCode    else return 0   to be honest this is from some old code I have  so you have to fiddle a bit with it   The cool thing though is that it reads input without prompting for anything  so the characters are not displayed at all

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CONIO H  the functions you need are   int getch    Prototype     int  getch void    Description      getch obtains a character  from stdin  Input is unbuffered  and this     routine  will  return as  soon as  a character is  available  without      waiting for a carriage return  The character is not echoed to stdout       getch bypasses the normal buffering done by getchar and getc  ungetc      cannot be used with  getch   Synonym     Function  getch    int kbhit    Description     Checks if a keyboard key has been pressed but not yet read   Return Value     Returns a non-zero value if a key was pressed  Otherwise  returns 0    libconio http   sourceforge net projects libconio  or  Linux c   implementation of conio h http   sourceforge net projects linux-conioh

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That s not possible in a portable manner in pure C    because it depends too much on the terminal used that may be connected with stdin  they are usually line buffered   You can  however use a library for that    conio available with Windows compilers  Use the  getch   function to give you a character without waiting for the Enter key  I m not a frequent Windows developer  but I ve seen my classmates just include  lt conio h gt  and use it  See conio h at Wikipedia  It lists getch    which is declared deprecated in Visual C     curses available for Linux  Compatible curses implementations are available for Windows too  It has also a getch   function   try man getch to view its manpage   See Curses at Wikipedia     I would recommend you to use curses if you aim for cross platform compatibility  That said  I m sure there are functions that you can use to switch off line buffering  I believe that s called  raw mode   as opposed to  cooked mode  - look into man stty   Curses would handle that for you in a portable manner  if I m not mistaken

User · Answer

Assuming Windows  take a look at the ReadConsoleInput function

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I use kbhit   to see if a char is present and then getchar   to read the data   On windows  you can use  conio h   On linux  you will have to implement your own kbhit     See code below      kbhit  include  lt stdio h gt   include  lt sys ioctl h gt     For FIONREAD  include  lt termios h gt   include  lt stdbool h gt   int kbhit void        static bool initflag   false      static const int STDIN   0       if   initflag               Use termios to turn off line buffering         struct termios term          tcgetattr STDIN   amp term           term c lflag  amp    ICANON          tcsetattr STDIN  TCSANOW   amp term           setbuf stdin  NULL           initflag   true             int nbbytes      ioctl STDIN  FIONREAD   amp nbbytes       0 is STDIN     return nbbytes        main  include  lt unistd h gt   int main int argc  char   argv        char c        setbuf stdout  NULL      Optional  No buffering        setbuf stdin  NULL       Optional  No buffering      printf  Press key        while   kbhit              printf               fflush stdout           sleep 1             c   getchar        printf   nChar received  c n   c       printf  Done  n         return 0

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ncurses provides a nice way to do this  Also this is my very first post  that I can remember   so any comments at all are welcome   I will appreciate useful ones  but all are welcome   to compile  g   -std c  11 -pthread -lncurses  cpp -o    include  lt iostream gt   include  lt ncurses h gt   include  lt future gt   char get keyboard input     int main int argc  char  argv          initscr        raw        noecho        keypad stdscr true        auto f   std  async std  launch  async  get keyboard input       while  f wait for std  chrono  milliseconds 20      std  future status  ready                   do some work            endwin        std  cout  lt  lt   returned     lt  lt  f get    lt  lt  std  endl      return 0     char get keyboard input         char input    0       while input     q                 input   getch              return input

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I always wanted a loop to read my input without pressing return key  this worked for me    include lt stdio h gt   main         char ch      system  stty raw     seting the terminal in raw mode     while 1              ch getchar          if ch                   terminate or come out of raw mode on     pressed       system  stty cooked           while 1    you may still run the code       exit 0     or terminate               printf  you pressed  c n   ch      write rest code here

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I always wanted a loop to read my input without pressing return key  this worked for me    include lt stdio h gt   main         char ch      system  stty raw     seting the terminal in raw mode     while 1              ch getchar          if ch                   terminate or come out of raw mode on     pressed       system  stty cooked           while 1    you may still run the code       exit 0     or terminate               printf  you pressed  c n   ch      write rest code here

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The closest thing to portable is to use the ncurses library to put the terminal into  cbreak mode    The API is gigantic  the routines you ll want most are   initscr and endwin cbreak and nocbreak getch   Good luck

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If you are on windows  you can use PeekConsoleInput to detect if there s any input    HANDLE handle   GetStdHandle STD INPUT HANDLE   DWORD events  INPUT RECORD buffer  PeekConsoleInput  handle   amp buffer  1   amp events      then use ReadConsoleInput to  consume  the input character     PeekConsoleInput handle   amp buffer  1   amp events   if events  gt  0        ReadConsoleInput handle   amp buffer  1   amp events         return buffer Event KeyEvent wVirtualKeyCode    else return 0   to be honest this is from some old code I have  so you have to fiddle a bit with it   The cool thing though is that it reads input without prompting for anything  so the characters are not displayed at all

User · Answer

Here s a version that doesn t shell out to the system  written and tested on macOS 10 14    include  lt unistd h gt   include  lt termios h gt   include  lt stdio h gt   include  lt string h gt   char  getStr  char  buffer   int maxRead       int  numRead    0    char ch     struct termios old    0     struct termios new    0     if  tcgetattr  0    amp old    lt  0          perror   tcgetattr   old settings       if  tcgetattr  0    amp new    lt  0          perror   tcgetaart   new settings       cfmakeraw   amp new      if  tcsetattr  0   TCSADRAIN    amp new    lt  0   perror   tcssetattr makeraw new        for  int i   0   i  lt  maxRead   i           ch   getchar        switch  ch            case EOF         case   n         case   r           goto exit getStr          break         default          printf    1c    ch            buffer  numRead       ch          if  numRead  gt   maxRead                goto exit getStr                    break             exit getStr    if  tcsetattr  0   TCSADRAIN    amp old   lt  0    perror   tcsetattr reset to old       printf    n          return buffer      int main  void        const int maxChars   20    char      stringBuffer  maxChars 1      memset    stringBuffer   0   maxChars 1       initialize to 0    printf   enter a string        getStr  stringBuffer   maxChars      printf   you entered    s  n    stringBuffer

User · Answer

The closest thing to portable is to use the ncurses library to put the terminal into  cbreak mode    The API is gigantic  the routines you ll want most are   initscr and endwin cbreak and nocbreak getch   Good luck

User · Answer

That s not possible in a portable manner in pure C    because it depends too much on the terminal used that may be connected with stdin  they are usually line buffered   You can  however use a library for that    conio available with Windows compilers  Use the  getch   function to give you a character without waiting for the Enter key  I m not a frequent Windows developer  but I ve seen my classmates just include  lt conio h gt  and use it  See conio h at Wikipedia  It lists getch    which is declared deprecated in Visual C     curses available for Linux  Compatible curses implementations are available for Windows too  It has also a getch   function   try man getch to view its manpage   See Curses at Wikipedia     I would recommend you to use curses if you aim for cross platform compatibility  That said  I m sure there are functions that you can use to switch off line buffering  I believe that s called  raw mode   as opposed to  cooked mode  - look into man stty   Curses would handle that for you in a portable manner  if I m not mistaken

User · Answer

CONIO H  the functions you need are   int getch    Prototype     int  getch void    Description      getch obtains a character  from stdin  Input is unbuffered  and this     routine  will  return as  soon as  a character is  available  without      waiting for a carriage return  The character is not echoed to stdout       getch bypasses the normal buffering done by getchar and getc  ungetc      cannot be used with  getch   Synonym     Function  getch    int kbhit    Description     Checks if a keyboard key has been pressed but not yet read   Return Value     Returns a non-zero value if a key was pressed  Otherwise  returns 0    libconio http   sourceforge net projects libconio  or  Linux c   implementation of conio h http   sourceforge net projects linux-conioh

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CONIO H  the functions you need are   int getch    Prototype     int  getch void    Description      getch obtains a character  from stdin  Input is unbuffered  and this     routine  will  return as  soon as  a character is  available  without      waiting for a carriage return  The character is not echoed to stdout       getch bypasses the normal buffering done by getchar and getc  ungetc      cannot be used with  getch   Synonym     Function  getch    int kbhit    Description     Checks if a keyboard key has been pressed but not yet read   Return Value     Returns a non-zero value if a key was pressed  Otherwise  returns 0    libconio http   sourceforge net projects libconio  or  Linux c   implementation of conio h http   sourceforge net projects linux-conioh

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works for me on windows    include  lt conio h gt  char c    getch

User · Answer

ncurses provides a nice way to do this  Also this is my very first post  that I can remember   so any comments at all are welcome   I will appreciate useful ones  but all are welcome   to compile  g   -std c  11 -pthread -lncurses  cpp -o    include  lt iostream gt   include  lt ncurses h gt   include  lt future gt   char get keyboard input     int main int argc  char  argv          initscr        raw        noecho        keypad stdscr true        auto f   std  async std  launch  async  get keyboard input       while  f wait for std  chrono  milliseconds 20      std  future status  ready                   do some work            endwin        std  cout  lt  lt   returned     lt  lt  f get    lt  lt  std  endl      return 0     char get keyboard input         char input    0       while input     q                 input   getch              return input

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On Linux  and other unix-like systems  this can be done in following way    include  lt unistd h gt   include  lt termios h gt   char getch             char buf   0          struct termios old    0           if  tcgetattr 0   amp old   lt  0                  perror  tcsetattr              old c lflag  amp    ICANON          old c lflag  amp    ECHO          old c cc VMIN    1          old c cc VTIME    0          if  tcsetattr 0  TCSANOW   amp old   lt  0                  perror  tcsetattr ICANON            if  read 0   amp buf  1   lt  0                  perror   read              old c lflag    ICANON          old c lflag    ECHO          if  tcsetattr 0  TCSADRAIN   amp old   lt  0                  perror   tcsetattr  ICANON            return  buf       Basically you have to turn off canonical mode  and echo mode to suppress echoing

User · Answer

That s not possible in a portable manner in pure C    because it depends too much on the terminal used that may be connected with stdin  they are usually line buffered   You can  however use a library for that    conio available with Windows compilers  Use the  getch   function to give you a character without waiting for the Enter key  I m not a frequent Windows developer  but I ve seen my classmates just include  lt conio h gt  and use it  See conio h at Wikipedia  It lists getch    which is declared deprecated in Visual C     curses available for Linux  Compatible curses implementations are available for Windows too  It has also a getch   function   try man getch to view its manpage   See Curses at Wikipedia     I would recommend you to use curses if you aim for cross platform compatibility  That said  I m sure there are functions that you can use to switch off line buffering  I believe that s called  raw mode   as opposed to  cooked mode  - look into man stty   Curses would handle that for you in a portable manner  if I m not mistaken

User · Answer

C and C   take a very abstract view of I O  and there is no standard way of doing what you want   There are standard ways to get characters from the standard input stream  if there are any to get  and nothing else is defined by either language   Any answer will therefore have to be platform-specific  perhaps depending not only on the operating system but also the software framework   There s some reasonable guesses here  but there s no way to answer your question without knowing what your target environment is

User · Answer

Assuming Windows  take a look at the ReadConsoleInput function

User · Answer

works for me on windows    include  lt conio h gt  char c    getch

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include  lt conio h gt   if  kbhit      0        cout  lt  lt  getch    lt  lt  endl      This uses kbhit   to check if the keyboard is being pressed and uses getch   to get the character that is being pressed

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You can do it portably using SDL  the Simple DirectMedia Library   though I suspect you may not like its behavior   When I tried it  I had to have SDL create a new video window  even though I didn t need it for my program  and have this window  grab  almost all keyboard and mouse input  which was okay for my usage but could be annoying or unworkable in other situations    I suspect it s overkill and not worth it unless complete portability is a must--otherwise try one of the other suggested solutions   By the way  this will give you key press and release events separately  if you re into that

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You can do it portably using SDL  the Simple DirectMedia Library   though I suspect you may not like its behavior   When I tried it  I had to have SDL create a new video window  even though I didn t need it for my program  and have this window  grab  almost all keyboard and mouse input  which was okay for my usage but could be annoying or unworkable in other situations    I suspect it s overkill and not worth it unless complete portability is a must--otherwise try one of the other suggested solutions   By the way  this will give you key press and release events separately  if you re into that

User · Answer

The following is a solution extracted from Expert C Programming  Deep Secrets  which is supposed to work on SVr4  It uses stty and ioctl      include  lt sys filio h gt  int kbhit      int i   ioctl 0  FIONREAD   amp i    return i     return a count of chars available to read      main      int i   0   intc      system  stty raw -echo     printf  enter  q  to quit  n     for   c   q  i          if  kbhit              c getchar           printf   n got  c  on iteration  d  c  i            system  stty cooked echo

User · Answer

C and C   take a very abstract view of I O  and there is no standard way of doing what you want   There are standard ways to get characters from the standard input stream  if there are any to get  and nothing else is defined by either language   Any answer will therefore have to be platform-specific  perhaps depending not only on the operating system but also the software framework   There s some reasonable guesses here  but there s no way to answer your question without knowing what your target environment is

User · Answer

include  lt conio h gt   if  kbhit      0        cout  lt  lt  getch    lt  lt  endl      This uses kbhit   to check if the keyboard is being pressed and uses getch   to get the character that is being pressed

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I found this on another forum while looking to solve the same problem  I ve modified it a bit from what I found  It works great  I m running OS X  so if you re running Microsoft  you ll need to find the correct system   command to switch to raw and cooked modes     include  lt iostream gt    include  lt stdio h gt    using namespace std     int main           Output prompt    cout  lt  lt   Press any key to continue      lt  lt  endl         Set terminal to raw mode    system  stty raw           Wait for single character    char input   getchar           Echo input    cout  lt  lt   --   lt  lt  input  lt  lt   --         Reset terminal to normal  cooked  mode    system  stty cooked           And we re out of here    return 0

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On Linux  and other unix-like systems  this can be done in following way    include  lt unistd h gt   include  lt termios h gt   char getch             char buf   0          struct termios old    0           if  tcgetattr 0   amp old   lt  0                  perror  tcsetattr              old c lflag  amp    ICANON          old c lflag  amp    ECHO          old c cc VMIN    1          old c cc VTIME    0          if  tcsetattr 0  TCSANOW   amp old   lt  0                  perror  tcsetattr ICANON            if  read 0   amp buf  1   lt  0                  perror   read              old c lflag    ICANON          old c lflag    ECHO          if  tcsetattr 0  TCSADRAIN   amp old   lt  0                  perror   tcsetattr  ICANON            return  buf       Basically you have to turn off canonical mode  and echo mode to suppress echoing

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I found this on another forum while looking to solve the same problem  I ve modified it a bit from what I found  It works great  I m running OS X  so if you re running Microsoft  you ll need to find the correct system   command to switch to raw and cooked modes     include  lt iostream gt    include  lt stdio h gt    using namespace std     int main           Output prompt    cout  lt  lt   Press any key to continue      lt  lt  endl         Set terminal to raw mode    system  stty raw           Wait for single character    char input   getchar           Echo input    cout  lt  lt   --   lt  lt  input  lt  lt   --         Reset terminal to normal  cooked  mode    system  stty cooked           And we re out of here    return 0

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The following is a solution extracted from Expert C Programming  Deep Secrets  which is supposed to work on SVr4  It uses stty and ioctl      include  lt sys filio h gt  int kbhit      int i   ioctl 0  FIONREAD   amp i    return i     return a count of chars available to read      main      int i   0   intc      system  stty raw -echo     printf  enter  q  to quit  n     for   c   q  i          if  kbhit              c getchar           printf   n got  c  on iteration  d  c  i            system  stty cooked echo

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If you are on windows  you can use PeekConsoleInput to detect if there s any input    HANDLE handle   GetStdHandle STD INPUT HANDLE   DWORD events  INPUT RECORD buffer  PeekConsoleInput  handle   amp buffer  1   amp events      then use ReadConsoleInput to  consume  the input character     PeekConsoleInput handle   amp buffer  1   amp events   if events  gt  0        ReadConsoleInput handle   amp buffer  1   amp events         return buffer Event KeyEvent wVirtualKeyCode    else return 0   to be honest this is from some old code I have  so you have to fiddle a bit with it   The cool thing though is that it reads input without prompting for anything  so the characters are not displayed at all

User · Answer

The closest thing to portable is to use the ncurses library to put the terminal into  cbreak mode    The API is gigantic  the routines you ll want most are   initscr and endwin cbreak and nocbreak getch   Good luck

User · Answer

C and C   take a very abstract view of I O  and there is no standard way of doing what you want   There are standard ways to get characters from the standard input stream  if there are any to get  and nothing else is defined by either language   Any answer will therefore have to be platform-specific  perhaps depending not only on the operating system but also the software framework   There s some reasonable guesses here  but there s no way to answer your question without knowing what your target environment is

User · Answer

CONIO H  the functions you need are   int getch    Prototype     int  getch void    Description      getch obtains a character  from stdin  Input is unbuffered  and this     routine  will  return as  soon as  a character is  available  without      waiting for a carriage return  The character is not echoed to stdout       getch bypasses the normal buffering done by getchar and getc  ungetc      cannot be used with  getch   Synonym     Function  getch    int kbhit    Description     Checks if a keyboard key has been pressed but not yet read   Return Value     Returns a non-zero value if a key was pressed  Otherwise  returns 0    libconio http   sourceforge net projects libconio  or  Linux c   implementation of conio h http   sourceforge net projects linux-conioh

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The following is a solution extracted from Expert C Programming  Deep Secrets  which is supposed to work on SVr4  It uses stty and ioctl      include  lt sys filio h gt  int kbhit      int i   ioctl 0  FIONREAD   amp i    return i     return a count of chars available to read      main      int i   0   intc      system  stty raw -echo     printf  enter  q  to quit  n     for   c   q  i          if  kbhit              c getchar           printf   n got  c  on iteration  d  c  i            system  stty cooked echo

User · Answer

The closest thing to portable is to use the ncurses library to put the terminal into  cbreak mode    The API is gigantic  the routines you ll want most are   initscr and endwin cbreak and nocbreak getch   Good luck

[c++] Capture characters from standard input without waiting for enter to be pressed

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