Add conditional support for -v / --verbose

[oweals/busybox.git] / coreutils / tail.c

diff --git a/coreutils/tail.c b/coreutils/tail.c
index fb07ca27b840515b6af11a0722f6220c0149b461..e352ab627b2e86b9e45c6ae59b1b17e4b0dd6ff1 100644 (file)
--- a/coreutils/tail.c
+++ b/coreutils/tail.c
@@ -25,7 +25,6 @@
  */
 
 //kbuild:lib-$(CONFIG_TAIL) += tail.o
-//kbuild:lib-$(CONFIG_TAIL) += head_tail.o
 
 //usage:#define tail_trivial_usage
 //usage:       "[OPTIONS] [FILE]..."
@@ -33,15 +32,14 @@
 //usage:       "Print last 10 lines of each FILE (or stdin) to stdout.\n"
 //usage:       "With more than one FILE, precede each with a filename header.\n"
 //usage:     "\n       -f              Print data as file grows"
-//usage:       IF_FEATURE_FANCY_TAIL(
-//usage:     "\n       -s SECONDS      Wait SECONDS between reads with -f"
-//usage:       )
+//usage:     "\n       -c [+]N[kbm]    Print last N bytes"
 //usage:     "\n       -n N[kbm]       Print last N lines"
 //usage:     "\n       -n +N[kbm]      Start on Nth line and print the rest"
 //usage:       IF_FEATURE_FANCY_TAIL(
-//usage:     "\n       -c [+]N[kbm]    Print last N bytes"
 //usage:     "\n       -q              Never print headers"
+//usage:     "\n       -s SECONDS      Wait SECONDS between reads with -f"
 //usage:     "\n       -v              Always print headers"
+//usage:     "\n       -F              Same as -f, but keep retrying"
 //usage:     "\n"
 //usage:     "\nN may be suffixed by k (x1024), b (x512), or m (x1024^2)."
 //usage:       )
@@ -51,7 +49,6 @@
 //usage:       "nameserver 10.0.0.1\n"
 
 #include "libbb.h"
-#include "head_tail.h"
 
 struct globals {
        bool from_top;
@@ -66,23 +63,10 @@ static void tail_xprint_header(const char *fmt, const char *filename)
                bb_perror_nomsg_and_die();
 }
 
-static ssize_t tail_read(int fd, char *buf, size_t count, int follow)
+static ssize_t tail_read(int fd, char *buf, size_t count)
 {
        ssize_t r;
 
-       if (follow) {
-               /* tail -f keeps following files even if they are truncated */
-               off_t current;
-               struct stat sbuf;
-
-               /* /proc files report zero st_size, don't lseek them */
-               if (fstat(fd, &sbuf) == 0 && sbuf.st_size > 0) {
-                       current = lseek(fd, 0, SEEK_CUR);
-                       if (sbuf.st_size < current)
-                               xlseek(fd, 0, SEEK_SET);
-               }
-       }
-
        r = full_read(fd, buf, count);
        if (r < 0) {
                bb_perror_msg(bb_msg_read_error);
@@ -102,7 +86,7 @@ static unsigned eat_num(const char *p)
                p++;
                G.from_top = 1;
        }
-       return xatou_sfx(p, head_tail_suffixes);
+       return xatou_sfx(p, bkm_suffixes);
 }
 
 int tail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
@@ -120,6 +104,7 @@ int tail_main(int argc, char **argv)
 
        int *fds;
        const char *fmt;
+       int prev_fd;
 
        INIT_G();
 
@@ -255,7 +240,7 @@ int tail_main(int argc, char **argv)
                 * Used only by +N code ("start from Nth", 1-based): */
                seen = 1;
                newlines_seen = 0;
-               while ((nread = tail_read(fd, buf, tailbufsize - taillen, /*follow:*/ 0)) > 0) {
+               while ((nread = tail_read(fd, buf, tailbufsize - taillen)) > 0) {
                        if (G.from_top) {
                                int nwrite = nread;
                                if (seen < count) {
@@ -324,6 +309,7 @@ int tail_main(int argc, char **argv)
                        xwrite(STDOUT_FILENO, tailbuf, taillen);
                }
        } while (++i < nfiles);
+       prev_fd = fds[i-1];
 
        tailbuf = xrealloc(tailbuf, BUFSIZ);
 
@@ -367,10 +353,23 @@ int tail_main(int argc, char **argv)
                        if (nfiles > header_threshhold) {
                                fmt = header_fmt_str;
                        }
-                       while ((nread = tail_read(fd, tailbuf, BUFSIZ, /*follow:*/ 1)) > 0) {
-                               if (fmt) {
+                       for (;;) {
+                               /* tail -f keeps following files even if they are truncated */
+                               struct stat sbuf;
+                               /* /proc files report zero st_size, don't lseek them */
+                               if (fstat(fd, &sbuf) == 0 && sbuf.st_size > 0) {
+                                       off_t current = lseek(fd, 0, SEEK_CUR);
+                                       if (sbuf.st_size < current)
+                                               xlseek(fd, 0, SEEK_SET);
+                               }
+
+                               nread = tail_read(fd, tailbuf, BUFSIZ);
+                               if (nread <= 0)
+                                       break;
+                               if (fmt && (fd != prev_fd)) {
                                        tail_xprint_header(fmt, filename);
                                        fmt = NULL;
+                                       prev_fd = fd;
                                }
                                xwrite(STDOUT_FILENO, tailbuf, nread);
                        }