I am trying to loop a char*str use this to find out how many lines:
char *str = "test1\ntest2\ntest3";
int lines = 0;
for(int i = 0 ; i < ?? ; i ++ )
{
if(str[i] == '\n') {
lines++;
}
}
I am not sure what to put at the ??, the question is :
1.I mean do I need to use strlen(str) + 1 ?
2.when the str is "test1\ntest2\ntest3\n",does the code still calculate correct lines?
I am using gcc by the way,thanks
every literal string ends with \0 which is a null character..It depicts the end of the string
So, You can do this
for(int i = 0 ; str[i]!='\0' ; i ++ )
To extend the already-existent good answers: the idiomatic way for looping through a C string is
const char *s = "abc\ndef\nghi\n";
int lines = 0;
int nonempty = 0;
while (*s) {
nonempty = 1;
if (*s++ == '\n') lines++;
}
If you don't want to count the last empty line as a separate line, then add
if (nonempty && s[-1] == '\n' && lines > 0) lines--;
after the while loop.
if (lines && s[-1] == '\n'); otherwise unpredictable for the empty string.nonempty rather than simply checking for lines > 0 (which implies nonempty) before s[-1]? As for s[-1] still being accessed, are you referring to some compiler-specific behaviour where optimizations might cause it to be accessed if it is guaranteed to not be a problem?Take the length of the string and iterate through all characters.
const unsigned long length=strlen(str);
for(int i = 0 ; i < length ; i ++ )
{
if(str[i] == '\n') {
lines++;
}
}
str[i] resp. str[i] != '\0' solution is better.The following will deliver the same result regardless if the last character is a newline or not.
char *abc = "test1\ntest2\ntest3";
int lines = 0;
{
bool lastWasNewline = true;
char * p = abc;
for (; *p; ++p) {
if (lastWasNewline) ++lines;
lastWasNewline = *p == '\n';
}
}
for statement is new to me. And then this test for strlen as loop condition is really, really not the the way to do it.1.I mean do I need to use strlen(str) + 1 ?
no, just use str[i] for i < ??, this tests if that is the 0 character which terminates the string
2.when the abc is "test1\ntest2\ntest3\n",does the code still calculate correct lines?
no, you code assumes that the input is broken into one input line per buffer line[j].
str[i] for ??, but use str[i] instead of i < ??.in place of ?? put strlen(abc) and make sure #include <string.h>
For better efficiency do
int length= strlen(abc);
and then use i < length
Or use str[i]!= '\0'
