...keep receiving characters until newline (enter key) is hit.Originally Posted by laserlight
...keep receiving characters until newline (enter key) is hit.
Okay. Why does this statement terminate as soon as enter key is hit?
Code:scanf("%[^\n]s %[^\n]s",str1,str2);
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Okay.. But aren't there two format strings. So isn't it supposed to keep receiving characters until enter is hit twice??
There are two format specifiers in a single format string.
The problem is probably that the newline is left in the input buffer after matching with the first format specifier, then it is used to match with the second format specifier. Anyway, you could just break the format string into two parts, i.e., use two scanf calls.
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I tried this statement and it worked. The only difference is that I removed the letter 's' from the format specifier...Why so???
Code:scanf("%[^\n] %[^\n]",str1,str2);
If we could give %[^] a name, it would be a scan set.
This string is a scan set all by itself:
"%[^\n]"
Now "%[^\n]s" is a scan set and the letter s, because every letter stands for itself, per the rules you learned. So %[^]s is not a special thing by itself.
Out of curiosity, but why did you try that statement?
What do you think?
Look, you have access to documentation too. What does it say? I am starting to suspect that I have been wrong in taking examples that I have seen at face value, but rather than jump the gun and tell you my reasoning, I want to hear yours.
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This is the code that I was writing, it is supposed to receive data for the structure blood and dump it into the file pointed by fp. But the loop terminates after the first run itself..
Code:#include<stdio.h> int main() { struct blood { char name[21]; char address[41]; int age, bt; }donor; FILE *fp; fp=fopen("acc.txt","w"); puts("Enter data"); while(scanf("%[^\n] %[^\n] %d %d",donor.name,donor.address,&donor.age,&donor.bt) == 4) fprintf(fp,"%s %s %d %d\n",donor.name,donor.address,donor.age,donor.bt); }
It's because scanf sucks.
There's virtually no reason to use scanf, to name a few:
- Dealing with newline characters is painful, whereas a fgets() call does not try to format it for you
- It's horrible for reading strings, as you cannot set the size limit which leads to segfaults, vulnerabilities in your code, or wasted memory
- It encourages programmers to be lazy by letting them read incredibly specific format strings (lets say you wanted a comma-delimited list of ints), without providing good error checking. In the case of reading a comma-delimited list of ints, scanf is ignoring the possibility that the user is entering invalid values, whereas splitting the string by commas, removing spaces, and using the if(!(num = atoi(chr))) syntax; is much easier to check for errors in the input
