1 files changed, 156 insertions, 0 deletions
diff --git a/src/minutils/s6-logwatch.c b/src/minutils/s6-logwatch.c
new file mode 100644
index 0000000..a2c493d
--- /dev/null
+++ b/src/minutils/s6-logwatch.c
@@ -0,0 +1,156 @@
+/* ISC license. */
+
+#include <errno.h>
+#include <unistd.h>
+#include <signal.h>
+#include <sys/ioctl.h>
+#include <sys/inotify.h>
+#include <skalibs/allreadwrite.h>
+#include <skalibs/sgetopt.h>
+#include <skalibs/bytestr.h>
+#include <skalibs/strerr2.h>
+#include <skalibs/error.h>
+#include <skalibs/buffer.h>
+#include <skalibs/bufalloc.h>
+#include <skalibs/sig.h>
+#include <skalibs/siovec.h>
+#include <skalibs/djbunix.h>
+#include <skalibs/iopause.h>
+#include <skalibs/ulong.h>
+
+#define USAGE "s6-logwatch [ -m maxbuffer ] logdir"
+#define dieusage() strerr_dieusage(100, USAGE)
+
+#define N 4096
+#define IESIZE 100
+
+typedef enum bstate_e bstate_t, *bstate_t_ref ;
+enum bstate_e
+{
+  B_TAILING = 0,
+  B_WAITING = 1
+} ;
+
+static void X (void)
+{
+  strerr_diefu1x(101, "follow file state changes (race condition triggered). Sorry.") ;
+}
+
+static unsigned long nbcat (int fdcurrent)
+{
+  char buf[N+1] ;
+  buffer b = BUFFER_INIT(&buffer_read, fdcurrent, buf, N+1) ;
+  siovec_t v[2] ;
+  unsigned long bytes = 0 ;
+  for (;;)
+  {
+    int r = sanitize_read(buffer_fill(&b)) ;
+    if (!r) break ;
+    if (r < 0)
+    {
+      if (errno == EPIPE) break ;
+      else strerr_diefu1sys(111, "buffer_fill") ;
+    }
+    buffer_rpeek(&b, v) ;
+    if (!bufalloc_putv(bufalloc_1, v, 2))
+      strerr_diefu1sys(111, "bufalloc_putv") ;
+    buffer_rseek(&b, r) ;
+    bytes += r ;
+  }
+  return bytes ;
+}
+
+
+int main (int argc, char const *const *argv)
+{
+  char const *dir = "." ;
+  unsigned long maxlen = 4000 ;
+  PROG = "s6-logwatch" ;
+  {
+    subgetopt_t l = SUBGETOPT_ZERO ;
+    for (;;)
+    {
+      register int opt = subgetopt_r(argc, argv, "m:", &l) ;
+      if (opt == -1) break ;
+      switch (opt)
+      {
+        case 'm' : if (!ulong0_scan(l.arg, &maxlen)) dieusage() ; break ;
+        default : dieusage() ;
+      }
+    }
+    argc -= l.ind ; argv += l.ind ;
+  }
+
+  if (argc) dir = *argv ;
+  if (chdir(dir) < 0) strerr_diefu2sys(111, "chdir to ", dir) ;
+  {
+    iopause_fd x[1] = { { -1, IOPAUSE_READ, 0 } } ;
+    int fdcurrent = -1 ;
+    unsigned long pos = 0 ;
+    int w ;
+    bstate_t state = B_TAILING ;
+    x[0].fd = inotify_init() ;
+    if (x[0].fd < 0) strerr_diefu1sys(111, "inotify_init") ;
+    if (ndelay_on(x[0].fd) < 0) strerr_diefu1sys(111, "ndelay_on inotify fd") ;
+    w = inotify_add_watch(x[0].fd, ".", IN_CREATE | IN_MODIFY | IN_CLOSE_WRITE) ;
+    if (w < 0) strerr_diefu1sys(111, "inotify_add_watch") ;
+    if (sig_ignore(SIGPIPE) == -1) strerr_diefu1sys(111, "sig_ignore(SIGPIPE)") ;
+    fdcurrent = open_readb("current") ;
+    if (fdcurrent < 0)
+      if (errno != ENOENT) strerr_diefu1sys(111, "open_readb current") ;
+      else state = B_WAITING ;
+    else pos = nbcat(fdcurrent) ;
+
+    for (;;)
+    {
+      int r ;
+      if (!bufalloc_flush(bufalloc_1)) strerr_diefu1sys(111, "write to stdout") ;
+      r = iopause(x, 1, 0, 0) ;
+      if (r < 0) strerr_diefu1sys(111, "iopause") ;
+      if (x[0].revents & IOPAUSE_READ)
+      {
+        char iebuf[IESIZE] ;
+        while (bufalloc_len(bufalloc_1) < maxlen)
+        {
+          unsigned int i = 0 ;
+          r = sanitize_read(fd_read(x[0].fd, iebuf, IESIZE)) ;
+          if (r < 0) strerr_diefu1sys(111, "read from inotify fd") ;
+          if (!r) break ;
+          while (i < (unsigned int)r)
+          {
+            struct inotify_event *ie = (struct inotify_event *)(iebuf + i) ;
+            if ((ie->wd != w) || !ie->len || str_diff(ie->name, "current")) goto cont ;
+            if (ie->mask & IN_MODIFY)
+            {
+              if (state) X() ;
+              pos += nbcat(fdcurrent) ;
+            }
+            else if (ie->mask & IN_CLOSE_WRITE)
+            {
+              if (state) X() ;
+              fd_close(fdcurrent) ;
+              fdcurrent = -1 ;
+              pos = 0 ;
+              state = B_WAITING ;
+            }
+            else if (ie->mask & IN_CREATE)
+            {
+              if (!state) X() ;
+              fdcurrent = open_readb("current") ;
+              if (fdcurrent < 0)
+              {
+                if (errno != ENOENT) strerr_diefu1sys(111, "open_readb current") ;
+                else goto cont ;
+              }
+              pos = nbcat(fdcurrent) ;
+              state = B_TAILING ;
+            }
+           cont:
+            i += sizeof(struct inotify_event) + ie->len ;
+          }
+        }
+      }
+    }
+  }
+  return 0 ;
+}