Search PATH for executables when running commands

This makes it easier for the user to run commands. Specifying abosolute
paths to a binary was kind of a pain in the rear.

man/man8/bpftrace.8

@@ -65,7 +65,7 @@ Enable USDT probes on PID. Will terminate bpftrace on PID termination. Note this
 .TP
 \fB\-c CMD\fR
 Helper to run CMD. Equivalent to manually running CMD and then giving passing the PID to -p. This is useful to ensure
-you've traced at least the duration CMD's execution. You must provide an absolute path for the executable.
+you've traced at least the duration CMD's execution.
 .
 .TP
 \fB\-v\fR

src/bpftrace.cpp

@@ -448,6 +448,7 @@ int BPFtrace::run(std::unique_ptr<BpfOrc> bpforc)
   if (cmd_.size())
   {
     auto args = split_string(cmd_, ' ');
+    args[0] = resolve_binary_path(args[0]);  // does path lookup on executable
     int pid = spawn_child(args);
     if (pid < 0)
     {
@@ -1111,6 +1112,28 @@ int BPFtrace::print_lhist(const std::vector<uint64_t> &values, int min, int max,
   return 0;
 }
 
+std::string BPFtrace::resolve_binary_path(const std::string& cmd)
+{
+  std::string query;
+  query += "command -pv ";
+  query += cmd;
+  std::string result = exec_system(query.c_str());
+
+  if (result.size())
+  {
+    // Remove newline at the end
+    auto it = result.rfind('\n');
+    if (it != std::string::npos)
+      result.erase(it);
+
+    return result;
+  }
+  else
+  {
+    return cmd;
+  }
+}
+
 int BPFtrace::spawn_child(const std::vector<std::string>& args)
 {
   static const int maxargs = 256;

src/bpftrace.h

@@ -120,6 +120,7 @@ private:
   static std::string lhist_index_label(int number);
   static std::vector<std::string> split_string(std::string &str, char split_by);
   std::vector<uint8_t> find_empty_key(IMap &map, size_t size) const;
+  static std::string resolve_binary_path(const std::string& cmd);
   static int spawn_child(const std::vector<std::string>& args);
   static bool is_pid_alive(int pid);
 };