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What happens to an open file handle on Linux if the pointed file gets moved or deleted
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void perror_and_exit() {
perror(NULL);
exit(1);
}
int main(int argc, char *argv[]) {
int fd;
if ((fd = open("data", O_RDONLY)) == -1) {
perror_and_exit();
}
char buf[5];
for (int i = 0; i < 5; i++) {
bzero(buf, 5);
if (read(fd, buf, 5) != 5) {
perror_and_exit();
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hash function for string
... had nice results with djb2 by Dan Bernstein.
unsigned long
hash(unsigned char *str)
{
unsigned long hash = 5381;
int c;
while (c = *str++)
hash = ((hash << 5) + hash) + c; /* hash * 33 + c */
return hash;
}
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Remove all occurrences of char from string
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Try using the overload that takes CharSequence arguments (eg, String) rather than char:
str = str.replace("X", "");
share
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Search text in fields in every table of a MySQL database
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If you have phpMyAdmin installed use its 'Search' feature.
Select your DB
Be sure you do have a DB selected (i.e. not a table, otherwise you'll get a completely different search dialog)
Click 'Search' tab
Choose the search term you want
Choose the tables to search
I have used this ...
How to printf uint64_t? Fails with: “spurious trailing ‘%’ in format”
... I wonder if there are progress towards a locale independent and/or locale selectable version of std::to_string(). The cppreference page still link only to std::to_chars(), which is not really what people need. I wonder if fmt and/or c++20 deal with it or not yet.
– ceztko
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Python Sets vs Lists
...from a sequence, and compute mathematical operations such as intersection, union, difference, and symmetric difference.
Usage
From some of the answers, it is clear that a list is quite faster than a set when iterating over the values. On the other hand, a set is faster than a list when checking if...
How do I remove all non alphanumeric characters from a string except dash?
How do I remove all non alphanumeric characters from a string except dash and space characters?
13 Answers
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Getting the first character of a string with $str[0]
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Yes. Strings can be seen as character arrays, and the way to access a position of an array is to use the [] operator. Usually there's no problem at all in using $str[0] (and I'm pretty sure is much faster than the substr() method).
There is only one ca...
How to concatenate twice with the C preprocessor and expand a macro as in “arg ## _ ## MACRO”?
...ER(x,y)
#define NAME(fun) EVALUATOR(fun, VARIABLE)
extern void NAME(mine)(char *x);
$ gcc -E xx.c
# 1 "xx.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "xx.c"
extern void mine_3(char *x);
$
Two levels of indirection
In a comment to another answer, Cade Roux asked why this needs t...
Why declare a struct that only contains an array in C?
...ever you declare such an object. This could also be achieved with
typedef char ABC[MAX];
but then you have a much bigger problem: you have to be aware that ABC is an array type (even though you can't see this when you declare variables of type ABC) or else you'll get stung by the fact that ABC wi...