Add ability to print process_env environment

3 files changed, 140 insertions, 1 deletions

diff --git a/libbutl/process-io.cxx b/libbutl/process-io.cxx
new file mode 100644
index 0000000..c29bbc0
--- /dev/null
+++ b/libbutl/process-io.cxx
@@ -0,0 +1,106 @@
+// file      : libbutl/process-io.cxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef __cpp_modules_ts
+#include <libbutl/process-io.mxx>
+#endif
+
+// C includes.
+
+#ifndef __cpp_lib_modules_ts
+#include <ostream>
+
+#include <cstring> // strchr()
+#endif
+
+// Other includes.
+
+#ifdef __cpp_modules_ts
+module butl.process_io;
+
+// Only imports additional to interface.
+#ifdef __clang__
+#ifdef __cpp_lib_modules_ts
+import std.core;
+import std.io;
+#endif
+import butl.process;
+#endif
+
+import butl.path-io;
+#else
+#include <libbutl/path-io.mxx>
+#endif
+
+using namespace std;
+
+namespace butl
+{
+  // process_env
+  //
+  ostream&
+  operator<< (ostream& o, const process_env& env)
+  {
+    bool first (true);
+    const dir_path* cwd (env.cwd);
+
+    if (cwd != nullptr && !cwd->empty ())
+    {
+      if (cwd->string ().find (' ') != string::npos)
+        o << "PWD=\"" << *cwd << '"';
+      else
+        o << "PWD=" << *cwd;
+
+      first = false;
+    }
+
+    if (env.vars != nullptr)
+    {
+      for (const char* const* ev (env.vars); *ev != nullptr; ++ev)
+      {
+        if (first)
+          first = false;
+        else
+          o << ' ';
+
+        const char* v (*ev);
+
+        // If there is no `=` in the string, then this is just a name
+        // (variable unset) and we print it as the empty string assignment.
+        //
+        const char* eq (strchr (v, '='));
+
+        // If there is the space character in the string, then we quote the
+        // variable value, unless this is the variable name that contains the
+        // space character in which case we quote the whole (potentially
+        // broken) assignment.
+        //
+        const char* sp (strchr (v, ' '));
+
+        if (eq != nullptr)             // Variable assignment?
+        {
+          if (sp == nullptr)           // No space?
+          {
+            o << v;
+          }
+          else if (eq < sp)            // Space in the value?
+          {
+            o.write (v, eq - v + 1);   // Name and '='.
+            o << '"' << eq + 1 << '"'; // Quoted value.
+          }
+          else                         // Space in the name.
+            o << '"' << v << '"';
+        }
+        else                           // Variable unset.
+        {
+          if (sp == nullptr)           // No space?
+            o << v << '=';
+          else                         // Space in the name.
+            o << '"' << v << "=\"";
+        }
+      }
+    }
+
+    return o;
+  }
+}
diff --git a/libbutl/process-io.mxx b/libbutl/process-io.mxx
index 5471846..d07a212 100644
--- a/libbutl/process-io.mxx
+++ b/libbutl/process-io.mxx
@@ -40,4 +40,28 @@ LIBBUTL_MODEXPORT namespace butl
     process::print (o, a.argv, a.argc);
     return o;
   }
+
+  // Print the environment variables and the current working directory (if
+  // specified) in a POSIX shell command line notation. The process path
+  // itself is not printed. For example:
+  //
+  // LC_ALL=C
+  //
+  // If an environment variable is in the `name` rather than in the
+  // `name=value` form, then it is considered unset. Since there is no POSIX
+  // way to unset a variable on the command line, this information is printed
+  // as `name=` (ambiguous with assigning an empty value but the two cases are
+  // normally handled in the same way). For example:
+  //
+  // PATH= LC_ALL=C
+  //
+  // Note that since there is no POSIX way to change the current working
+  // directory of a command to be executed, this information is printed in a
+  // pseudo-notation by assigning to PWD (which, according POSIX, would result
+  // in the undefined behavior of the cwd utility). For example:
+  //
+  // PWD=/tmp LC_ALL=C
+  //
+  LIBBUTL_SYMEXPORT std::ostream&
+  operator<< (std::ostream&, const process_env&);
 }
diff --git a/libbutl/process.mxx b/libbutl/process.mxx
index 1f378c4..b8c6054 100644
--- a/libbutl/process.mxx
+++ b/libbutl/process.mxx
@@ -494,7 +494,6 @@ LIBBUTL_MODEXPORT namespace butl
     quote_argument (const char*, std::string& buffer);
 #endif
 
-
   public:
     id_type
     id () const;
@@ -548,6 +547,16 @@ LIBBUTL_MODEXPORT namespace butl
     const dir_path*     cwd  = nullptr;
     const char* const*  vars = nullptr;
 
+    // Return true if there is an "environment", that is, either the current
+    // working directory or environment variables.
+    //
+    bool
+    env () const
+    {
+      return (cwd != nullptr && !cwd->empty ()) ||
+             (vars != nullptr && *vars != nullptr);
+    }
+
     process_env (const process_path& p,
                  const dir_path& c = dir_path (),
                  const char* const* v = nullptr)