Editing strings
Author
I am trying to create a few commands for my console app when I ran into the problem about editing the command to do specific functions on user input. For example, I have a "-say" and a "-do" command. the say command would make the console output whatever string I input after "-say"(for example, "-say Hello World!"). The problem I ran into is stripping the string if the command whenever it's needed. One solution I tried was using a normal string (char str[];) then doing str += 5; to remove the first 5 characters. That way doesn't work all the time though, so if i typed in the console, -shu hello world!, the command would still think I said -say hello world. In general, what I need is a way to remove a string from the input(the string being "-say " or "-do "(with the space included)). Thanks
So, I understand you are using C.
Step 2: remove the first 5 characters and display (you already did that).
Step 1: check that the four first characters are '-', 's', 'a' and 'y'.
Step 2: remove the first 5 characters and display (you already did that).
Step 1: check that the four first characters are '-', 's', 'a' and 'y'.
Quote:In general, what I need is a way to remove a string from the input(the string being "-say " or "-do "(with the space included)).
Is the string always at the start of the string, also is it guarenteed that the string is only one time in the input?
If it's always at the start you can do something like this (basically what ToohrVyk said, just in a function):
bool is_equal_fixed(char* str1,char* str2,size_t len){ assert( strlen(str1) >= len ); assert( strlen(str2) >= len ); for( int i = 0;i<len;++i) { if( str1 != str2 ) return false; } return true;}bool starts_with(char* input,char* command){ // is size_t a C type? size_t cmd_length = strlen(command); // Make sure input is longer than the command. assert(cmd_length <= strlen(input) ); return is_equal_fixed(input,command,cmd_length);}EDIT: If I understand your description right, then you do something like the following:
char str[255]; // Input cant be longer than 255get_input(str);char* out = 0;if( starts_with_say(str ) ){ out = (str+5);}If that is basically what you are doing then you can run into a problem if str is deleted before we are done using out.
This is a simple proble with a really simple solution, lets not try to over complicate it fellas.
This works just fine
This works just fine
if (str == strstr(str, "-say")){ printf("%s\n", (str+5));}
Actually, I realized me and Thetan made a mistake and forgot to include the fifth character (space) in the checking.
your absolutely right. if we disregard the trailing space, we run the possiblity of the user submitting just "-say" and running *("-say"+5), will leave us with a pointer directly after the end of the buffer passed the null-byte even, so who knows what this would return.
The correct code would be
The correct code would be
if (str == strstr(str, "-say ")){ printf("%s\n", (str+5));}This topic is closed to new replies.
Advertisement
Popular Topics
Advertisement
