1 files changed, 145 insertions, 0 deletions
diff --git a/src/skaembutils/s6-ln.c b/src/skaembutils/s6-ln.c
new file mode 100644
index 0000000..7f6f7b6
--- /dev/null
+++ b/src/skaembutils/s6-ln.c
@@ -0,0 +1,145 @@
+/* ISC license. */
+
+#include <skalibs/sysdeps.h>
+
+#ifdef SKALIBS_HASLINKAT
+#include <skalibs/nonposix.h>
+#endif
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+#include <stdio.h>
+#include <skalibs/sgetopt.h>
+#include <skalibs/bytestr.h>
+#include <skalibs/strerr2.h>
+#include <skalibs/stralloc.h>
+#include <skalibs/djbunix.h>
+#include <skalibs/random.h>
+#include <skalibs/skamisc.h>
+
+#define USAGE "s6-ln [ -s ] [ -f ] [ -L ] [ -P ] src... dest"
+
+typedef int linkfunc_t (char const *, char const *) ;
+typedef linkfunc_t *linkfunc_t_ref ;
+
+typedef void ln_t (char const *, char const *, linkfunc_t_ref) ;
+typedef ln_t *ln_t_ref ;
+
+#ifdef SKALIBS_HASLINKAT
+
+static int linknoderef (char const *old, char const *new)
+{
+  return linkat(AT_FDCWD, old, AT_FDCWD, new, 0) ;
+}
+
+static int linkderef (char const *old, char const *new)
+{
+  return linkat(AT_FDCWD, old, AT_FDCWD, new, AT_SYMLINK_FOLLOW) ;
+}
+
+#else /* can't implement SUSv4, default to link */
+
+# define linknoderef link
+# define linkderef link
+
+#endif
+
+static void force (char const *old, char const *new, linkfunc_t_ref doit)
+{
+  if ((*doit)(old, new) == -1)
+  {
+    unsigned int base = satmp.len ;
+    if (errno != EEXIST)
+      strerr_diefu5sys(111, "make a link", " from ", new, " to ", old) ;
+    if (!stralloc_catb(&satmp, new, str_len(new))
+     || (random_sauniquename(&satmp, 8) == -1)
+     || !stralloc_0(&satmp))
+      strerr_diefu2sys(111, "make a unique name for ", old) ;
+    if ((*doit)(old, satmp.s + base) == -1)
+      strerr_diefu3sys(111, "make a link", " to ", old) ;
+    if (rename(satmp.s + base, new) == -1)
+    {
+      unlink(satmp.s + base) ;
+      strerr_diefu2sys(111, "atomically replace ", new) ;
+    }
+    satmp.len = base ;
+  }
+}
+
+static void noforce (char const *old, char const *new, linkfunc_t_ref doit)
+{
+  if ((*doit)(old, new) == -1)
+    strerr_diefu5sys(111, "make a link", " from ", new, " to ", old) ;
+}
+
+int main (int argc, char const *const *argv)
+{
+  linkfunc_t_ref mylink = &link ; /* default to system behaviour */
+  ln_t_ref f = &noforce ;
+  PROG = "s6-ln" ;
+  {
+    subgetopt_t l = SUBGETOPT_ZERO ;
+    for (;;)
+    {
+      register int opt = subgetopt_r(argc, argv, "sfLP", &l) ;
+      if (opt == -1) break ;
+      switch (opt)
+      {
+        case 's': mylink = &symlink ; break ;
+        case 'f': f = &force ; break ;
+        case 'L': if (mylink != &symlink) mylink = &linkderef ; break ;
+        case 'P': if (mylink != &symlink) mylink = &linknoderef ; break ;
+        default : strerr_dieusage(100, USAGE) ;
+      }
+    }
+    argc -= l.ind ; argv += l.ind ;
+  }
+  if (argc < 2) strerr_dieusage(100, USAGE) ;
+  if (argc > 2)
+  {
+    stralloc sa = STRALLOC_ZERO ;
+    unsigned int i = 0 ;
+    unsigned int base ;
+    if (!stralloc_cats(&sa, argv[argc-1]) || !stralloc_catb(&sa, "/", 1))
+      strerr_diefu1sys(111, "stralloc_cats") ;
+    base = sa.len ;
+    for (; i < (unsigned int)(argc-1) ; i++)
+    {
+      sa.len = base ;
+      if (!sabasename(&sa, argv[i], str_len(argv[i])))
+        strerr_diefu1sys(111, "sabasename") ;
+      if (!stralloc_0(&sa)) strerr_diefu1sys(111, "stralloc_0") ;
+      (*f)(argv[i], sa.s, mylink) ;
+    }
+    return 0 ;
+  }
+
+  {
+    struct stat st ;
+    if (stat(argv[1], &st) < 0)
+    {
+      if (errno != ENOENT) strerr_diefu2sys(111, "stat ", argv[1]) ;
+      (*f)(argv[0], argv[1], mylink) ;
+      return 0 ;
+    }
+    if (!S_ISDIR(st.st_mode))
+    {
+      (*f)(argv[0], argv[1], mylink) ;
+      return 0 ;
+    }
+  }
+
+  {
+    stralloc sa = STRALLOC_ZERO ;
+    if (!stralloc_cats(&sa, argv[1])
+      || !stralloc_catb(&sa, "/", 1)
+      || !sabasename(&sa, argv[0], str_len(argv[0]))
+      || !stralloc_0(&sa))
+        strerr_diefu1sys(111, "stralloc_catb") ;
+      (*f)(argv[0], sa.s, mylink) ;
+  }
+  return 0 ;
+}