You are failing to access a field of the indexed union array: mydata[0] is a value of type union data, and can’t be cast to uint64_t. You need to access the proper union member: to select the uint64_t value. No need for the cast. Also: Use PRIu64 to portably print 64-bit values, you can’t assume … Read more
According to the standard (§6.4.4.4/10) The value of an integer character constant containing more than one character (e.g., ‘ab’), […] is implementation-defined. This is valid ISO 9899:2011 C. It compiles without warning under gcc with -Wall, and a “multi-character character constant” warning with -pedantic. From Wikipedia: Multi-character constants (e.g. ‘xy’) are valid, although rarely useful … Read more
I’m hoping someone could shed some light on how to make the parent wait for ALL child processes to finish before continuing after the fork. I have cleanup code which I want to run but the child processes need to have returned before this can happen.
num will always contain an integer because it’s an int. The real problem with your code is that you don’t check the scanf return value. scanf returns the number of successfully read items, so in this case it must return 1 for valid values. If not, an invalid integer value was entered and the num … Read more
You’re saying you have this: And you’d like to have this: You can’t have that. A char holds 1 character. That’s it. A “string” in C is an array of characters followed by a sentinel character (NULL terminator). Now if you want to copy the first x characters out of array to string you can … Read more
0x01 is the least significant bit set, hence the decimal value is 1. 0x80 is the most significant bit of an 8-bit byte set. If it is stored in a signed char (on a machine that uses 2’s-complement notation – as most machines you are likely to come across will), it is the most negative … Read more
Flushing the output buffers: or Can be a very helpful technique. Why would you want to flush an output buffer? Usually when I do it, it’s because the code is crashing and I’m trying to debug something. The standard buffer will not print everytime you call printf() it waits until it’s full then dumps a bunch at … Read more
You need to include the appropriate header If you’re not sure which header a standard function is defined in, the function’s man page will state this.
Change the line where you print the output to: See the docs here
Wow, a lot of big OOP terms being thrown around to this guy. Being one who started in procedural programming and is now mostly doing OOP, this is conceptually how I think of the difference (without all the big terms): In C, you have things called structs that can hold state. They kind of seem … Read more