Setting an array to one value

Question

Is there an easier way in C to set an array to one value than using a for loop and going setting each value one by one?

Answer 1

If it's an array of byte values, or you want to set each byte to a specific value, you can use memset:

char xyzzy[100];
int plugh[40];
memset (xyzzy, 7, sizeof (xyzzy)); // all chars set to 7.
memset (plugh, 0x42, sizeof (plugh));  // all integers set to (e.g.) 0x42424242.

Another possibility is to create a template of the correct size at initialisation time (either real initialisation as per below, or in an init function), then call memcpy to blat ^(a) it onto the real array at a later date.

static int template[] = { 1, 1, 1, 1, 1 };
int zorkmid[3];
memcpy (zorkmid, template, sizeof (zorkmid)); // ensure template is at
                                              // least as big as zorkmid.

This latter method is also handy for populating structures with a fixed pre-calculated value: initialise a dummy copy with the required fields set then memcpy it instead of manually setting all the fields each time you want a new instance.

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^(a) Aside: etymology of blat:

The Jargon file (see the glossary for all the definitions) lists blat as either the four metasyntactic variable {foo, bar, thud, blat}, or a synonym for blast, sense 1.

In turn, blast (sense 1) is defined as a synonym of BLT (that's not the sandwich), which "referred to any large bit-field copy or move operation".