diff options
Diffstat (limited to 'coreutils/shuf.c')
| -rw-r--r-- | coreutils/shuf.c | 29 |
1 files changed, 15 insertions, 14 deletions
diff --git a/coreutils/shuf.c b/coreutils/shuf.c index fdbd3e9..3b2ba93 100644 --- a/coreutils/shuf.c +++ b/coreutils/shuf.c @@ -24,7 +24,7 @@ //usage: "\n -i L-H Treat numbers L-H as lines" //usage: "\n -n NUM Output at most NUM lines" //usage: "\n -o FILE Write to FILE, not standard output" -//usage: "\n -z End lines with zero byte, not newline" +//usage: "\n -z NUL terminated output" #include "libbb.h" @@ -39,8 +39,10 @@ /* * Use the Fisher-Yates shuffle algorithm on an array of lines. + * If the required number of output lines is less than the total + * we can stop shuffling early. */ -static void shuffle_lines(char **lines, unsigned numlines) +static void shuffle_lines(char **lines, unsigned numlines, unsigned outlines) { unsigned i; unsigned r; @@ -48,7 +50,7 @@ static void shuffle_lines(char **lines, unsigned numlines) srand(monotonic_us()); - for (i = numlines-1; i > 0; i--) { + for (i = numlines-1; outlines > 0; i--, outlines--) { r = rand(); /* RAND_MAX can be as small as 32767 */ if (i > RAND_MAX) @@ -67,7 +69,7 @@ int shuf_main(int argc, char **argv) char *opt_i_str, *opt_n_str, *opt_o_str; unsigned i; char **lines; - unsigned numlines; + unsigned numlines, outlines; char eol; opts = getopt32(argv, "^" @@ -128,24 +130,23 @@ int shuf_main(int argc, char **argv) fclose_if_not_stdin(fp); } - if (numlines != 0) - shuffle_lines(lines, numlines); + outlines = numlines; + if (opts & OPT_n) { + outlines = xatou(opt_n_str); + if (outlines > numlines) + outlines = numlines; + } + + shuffle_lines(lines, numlines, outlines); if (opts & OPT_o) xmove_fd(xopen(opt_o_str, O_WRONLY|O_CREAT|O_TRUNC), STDOUT_FILENO); - if (opts & OPT_n) { - unsigned maxlines; - maxlines = xatou(opt_n_str); - if (numlines > maxlines) - numlines = maxlines; - } - eol = '\n'; if (opts & OPT_z) eol = '\0'; - for (i = 0; i < numlines; i++) { + for (i = numlines - outlines; i < numlines; i++) { if (opts & OPT_i) printf("%u%c", (unsigned)(uintptr_t)lines[i], eol); else |