Erase the current printed console line

Question

How can I erase the current printed console line in C  I am working on a Linux system  For example -   printf  hello    printf  bye      I want to print bye on the same line in place of hello

User · Answer

echo -e  hello c   sleep 1   echo -e   rbye      What the above command will do     It will print hello and the cursor will remain at  o   using  c  Then it will wait for 1 sec  sleep 1  Then it will replace hello with bye  using  r    NOTE   Using      We can run multiple command in a single go

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Just found this old thread  looking for some kind of escape sequence to blank the actual line    It s quite funny no one came to the idea  or I have missed it  that printf returns the number of characters written  So just print   r    as many blank characters as printf returned and you will exactly blank the previuosly written text   int BlankBytes int Bytes                    char strBlankStr 16                    sprintf strBlankStr    r   is r   Bytes                   printf strBlankStr                       return 0     int main void                    int iBytesWritten                  double lfSomeDouble   150 0                   iBytesWritten   printf  test text  lf   lfSomeDouble                    BlankBytes iBytesWritten                    return 0      As I cant use VT100  it seems I have to stick with that solution

User · Answer

You can use VT100 escape codes  Most terminals  including xterm  are VT100 aware  For erasing a line  this is    2K  In C this gives   printf   c 2K   27

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This script is hardcoded for your example    include  lt stdio h gt   int main             write some input       fputs  hello n  stdout          wait one second to change line above     sleep 1          remove line     fputs   033 A 033 2K  stdout       rewind stdout          write new line     fputs  bye n  stdout        return 0      Click here for source

User · Answer

there is a simple trick you can work here but it need preparation before you print  you have to put what ever you wants to print in a variable and then print so you will know the length to remove the string here is an example    include  lt iostream gt   include  lt string gt    actually this thing is not nessasory in tdm-gcc  using namespace  std   int main       create string variable  string str  Starting count      loop for printing numbers      for int i  0 i lt  50000 i                get previous string length and clear it from screen with backspace charactor          cout  lt  lt  string str length     b               create string line          str  Starting count    to string i              print the new line in same spot          cout  lt  lt str

User · Answer

under windows 10 one can use VT100 style by activating the VT100 mode in the current console to use escape sequences as follow     include  lt windows h gt   include  lt iostream gt    define ENABLE VIRTUAL TERMINAL PROCESSING 0x0004  define DISABLE NEWLINE AUTO RETURN  0x0008  int main          enabling VT100 style in current console   DWORD l mode    HANDLE hStdout   GetStdHandle STD OUTPUT HANDLE     GetConsoleMode hStdout  amp l mode    SetConsoleMode  hStdout  l mode               ENABLE VIRTUAL TERMINAL PROCESSING               DISABLE NEWLINE AUTO RETURN          create a waiting loop with changing text every seconds   while true           erase current line and go to line begining      std  cout  lt  lt    x1B 2K r       std  cout  lt  lt   wait a second         Sleep 1       std  cout  lt  lt    x1B 2K r       std  cout  lt  lt   wait a second          Sleep 1       std  cout  lt  lt    x1B 2K r       std  cout  lt  lt   wait a second           Sleep 1       std  cout  lt  lt    x1B 2K r       std  cout  lt  lt   wait a second                see following link   windows VT100

User · Answer

Some worthwhile subtleties      33 2K erases the entire line your cursor is currently on   033 A moves your cursor up one line  but in the same column i e  not to the start of the line   r brings your cursor to the beginning of the line  r is for carriage return N B  carriage returns do not include a newline so cursor remains on the same line  but does not erase anything  In xterm specifically  I tried the replies mentioned above and the only way I found to erase the line and start again at the beginning is the sequence  from the comment above posted by  Stephan202 as well as  vlp and  mantal   33 2K r  On an implementation note  to get it to work properly for example in a countdown scenario since I wasn t using a new line character   n  at the end of each fprintf    so I had to fflush   the stream each time  to give you some context  I started xterm using a fork on a linux machine without redirecting stdout  I was just writing to the buffered FILE pointer fdfile with a non-blocking file descriptor I had sitting on the pseudo terminal address which in my case was  dev pts 21    fprintf fdfile    33 2K rT minus  d seconds      i   fflush fdfile     Note that I used both the  33 2K sequence to erase the line followed by the  r carriage return sequence to reposition the cursor at the beginning of the line  I had to fflush   after each fprintf   because I don t have a new line character at the end   n   The same result without needing fflush   would require the additional sequence to go up a line   fprintf fdfile    033 A 33 2K rT minus  d seconds    n   i     Note that if you have something on the line immediately above the line you want to write on  it will get over-written with the first fprintf    You would have to leave an extra line above to allow for the first movement up one line   i   3  fprintf fdfile    nText to keep n    fprintf fdfile   Text to erase                             n    while i  gt  0       3 second countdown     fprintf fdfile    033 A 33 2KT rT minus  d seconds    n   i       i--      sleep 1

User · Answer

i iterates through char array words   j keeps track of word length     b  b  erases word while backing over line    include lt stdio h gt   int main         int i   0  j   0       char words      Hello Bye        while words i     0                 if words i                        printf   c   words i            fflush stdout                     else                 system  ping -n 1 127 0 0 1 gt NUL       For Microsoft OS             system  sleep 0 25                while j-- gt 0                    printf   b  b                                     i            j           printf   n                       return 0

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Usually when you have a   r  at the end of the string  only carriage return is printed without any newline  If you have the following   printf  fooooo r    printf  bar      the output will be   barooo   One thing I can suggest  maybe a workaround  is to have a NULL terminated fixed size string that is initialized to all space characters  ending in a   r   every time before printing   and then use strcpy to copy your string into it  without the newline   so every subsequent print will overwrite the previous string  Something like this   char str MAX LENGTH              init str to all spaces  NULL terminated with character as   r  strcpy str  my string            copy my string into str str strlen my string             erase null termination char str MAX LENGTH - 1      r   printf str     You can do error checking so that my string is always atleast one less in length than str  but you get the basic idea

User · Answer

You could delete the line using  b  printf  hello    int i  for  i 0  i lt 80  i        printf   b      printf  bye

User · Answer

You can use a  r  carriage return  to return the cursor to the beginning of the line   printf  hello    printf   rbye      This will print bye on the same line  It won t erase the existing characters though  and because bye is shorter than hello  you will end up with byelo  To erase it you can make your new print longer to overwrite the extra characters   printf  hello    printf   rbye        Or  first erase it with a few spaces  then print your new string   printf  hello    printf   r              printf   rbye      That will print hello  then go to the beginning of the line and overwrite it with spaces  then go back to the beginning again and print bye

[c] Erase the current printed console line

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