diff options
| -rw-r--r-- | doc_src/random.txt | 16 | ||||
| -rw-r--r-- | src/builtin.cpp | 6 |
2 files changed, 16 insertions, 6 deletions
diff --git a/doc_src/random.txt b/doc_src/random.txt index 5e50232a..24b7b545 100644 --- a/doc_src/random.txt +++ b/doc_src/random.txt @@ -7,9 +7,19 @@ random [SEED] \subsection random-description Description -`random` outputs a random number from 0 to 32766, inclusive. - -If a `SEED` value is provided, it is used to seed the random number generator, and no output will be produced. This can be useful for debugging purposes, where it can be desirable to get the same random number sequence multiple times. If the random number generator is called without first seeding it, the current time will be used as the seed. +`random` outputs a psuedo-random number from 0 to 32767, inclusive. +Even ignoring the very narrow range of values you should not assume +this produces truly random values within that range. Do not use the +value for any cryptographic purposes. Even if you're using it to, for +example, generate unique identifiers you should be careful about handling +collisions; i.e., the same random number appearing more than once in a +given fish instance. + +If a `SEED` value is provided, it is used to seed the random number +generator, and no output will be produced. This can be useful for debugging +purposes, where it can be desirable to get the same random number sequence +multiple times. If the random number generator is called without first +seeding it, the current time will be used as the seed. \subsection random-example Example diff --git a/src/builtin.cpp b/src/builtin.cpp index 932cf1b8..991c33da 100644 --- a/src/builtin.cpp +++ b/src/builtin.cpp @@ -2345,7 +2345,6 @@ static int builtin_random(parser_t &parser, io_streams_t &streams, wchar_t **arg switch (argc-w.woptind) { - case 0: { long res; @@ -2356,8 +2355,9 @@ static int builtin_random(parser_t &parser, io_streams_t &streams, wchar_t **arg srand48_r(time(0), &seed_buffer); } lrand48_r(&seed_buffer, &res); - - streams.out.append_format( L"%ld\n", labs(res%32767)); + // The labs() shouldn't be necessary since lrand48 is supposed to + // return only positive integers but we're going to play it safe. + streams.out.append_format(L"%ld\n", labs(res % 32768)); break; } |