1 files changed, 84 insertions, 0 deletions
diff --git a/src/execline/backtick.c b/src/execline/backtick.c
new file mode 100644
index 0000000..d0f74e4
--- /dev/null
+++ b/src/execline/backtick.c
@@ -0,0 +1,84 @@
+/* ISC license. */
+
+#include <sys/types.h>
+#include <unistd.h>
+#include <skalibs/bytestr.h>
+#include <skalibs/sgetopt.h>
+#include <skalibs/strerr2.h>
+#include <skalibs/stralloc.h>
+#include <skalibs/djbunix.h>
+#include <execline/execline.h>
+
+#define USAGE "backtick [ -i ] [ -n ] var { prog... } remainder..."
+#define dieusage() strerr_dieusage(100, USAGE)
+
+int main (int argc, char const **argv, char const *const *envp)
+{
+  subgetopt_t localopt = SUBGETOPT_ZERO ;
+  int argc1 ;
+  stralloc modif = STRALLOC_ZERO ;
+  int insist = 0, chomp = 0 ;
+  PROG = "backtick" ;
+  for (;;)
+  {
+    register int opt = subgetopt_r(argc, argv, "ein", &localopt) ;
+    if (opt < 0) break ;
+    switch (opt)
+    {
+      case 'i' : insist = 1 ; break ;
+      case 'n' : chomp = 1 ; break ;
+      case 'e' : break ; /* compat */
+      default : dieusage() ;
+    }
+  }
+  argc -= localopt.ind ; argv += localopt.ind ;
+
+  if (argc < 2) dieusage() ;
+  if (!*argv[0]) strerr_dief1x(100, "empty variable not accepted") ;
+  if (!stralloc_cats(&modif, argv[0]) || !stralloc_catb(&modif, "=", 1))
+    strerr_diefu1sys(111, "stralloc_catb") ;
+  argc-- ; argv++ ;
+  argc1 = el_semicolon(argv) ;
+  if (!argc1) strerr_dief1x(100, "empty block") ;
+  if (argc1 >= argc) strerr_dief1x(100, "unterminated block") ;
+
+  {
+    int p[2] ;
+    pid_t pid ;
+    if (pipe(p) < 0) strerr_diefu1sys(111, "pipe") ;
+    pid = fork() ;
+    switch (pid)
+    {
+      case -1: strerr_diefu1sys(111, "fork") ;
+      case 0:
+        argv[argc1] = 0 ;
+        fd_close(p[0]) ;
+        PROG = "backtick (child)" ;
+        if (fd_move(1, p[1]) < 0) strerr_diefu1sys(111, "fd_move") ;
+        pathexec_run(argv[0], argv, envp) ;
+        strerr_dieexec(111, argv[0]) ;
+    }
+    fd_close(p[1]) ;
+    if (!slurp(&modif, p[0])) strerr_diefu1sys(111, "slurp") ;
+    fd_close(p[0]) ;
+    if (wait_pid(pid, &p[0]) < 0) strerr_diefu1sys(111, "wait_pid") ;
+    if (insist && wait_status(p[0]))
+      strerr_dief1x(wait_status(p[0]), "child process exited non-zero") ;
+  }
+  if (argc == argc1 - 1) return 0 ;
+  if (!stralloc_0(&modif)) strerr_diefu1sys(111, "stralloc_catb") ;
+  {
+    unsigned int reallen = str_len(modif.s) ;
+    if (reallen < modif.len - 1)
+    {
+      if (insist)
+        strerr_dief1x(1, "child process output contained a null character") ;
+      else
+        modif.len = reallen + 1 ;
+    }
+    if (chomp && (modif.s[modif.len - 2] == '\n'))
+      modif.s[--modif.len - 1] = 0 ;
+  }
+  pathexec_r(argv + argc1 + 1, envp, env_len(envp), modif.s, modif.len) ;
+  strerr_dieexec(111, argv[argc1 + 1]) ;
+}