Test whether Gnuplot supports X11.

pub/lib/dualplot.cpp

@@ -40,6 +40,13 @@ CPlot::CPlot( int _iPlot, bool _logx, bool _logy ) :
     if (mkfifo( fn_fifo.c_str(), 0666 ))
         throw "SYSTEM ERROR cannot make fifo "+fn_fifo+": will not be able to print";
 
+    // Check that Gnuplot supports X11.
+    string out = triv::system_read( "gnuplot -e 'help X11' 2>&1 < /dev/null" );
+    if ( out.substr(0,5)=="Sorry" || out.length()<80 ) {
+        cerr << "Gnuplot seems not to support X11\n";
+        exit(1);
+    }
+    
     // Start a Gnuplot that will read from our pipe.
     triv::system( "gnuplot -title "+S(iPlot)+" -noraise < "+fn_fifo+"&" );
 

pub/trivia/file_ops.cpp

@@ -40,6 +40,23 @@ void triv::system( string cmd, bool debug )
         cout << "DEBUG system call -> return value " << ret << "\n";
 }
 
+//! Execute operation system call, and return its stdout.
+
+string triv::system_read( string cmd, bool debug )
+{
+    if( debug )
+        cout << "DEBUG system call '" + cmd + "'\n";
+    FILE *f = ::popen( cmd.c_str(), "r" );
+
+    string ret;
+    char buf[1024];
+    while( fgets( buf, 1024, f ) )
+        ret += buf;
+
+    pclose( f );
+    return ret;
+}
+
 
 //**************************************************************************//
 //*  file names, globbing                                                  *//

pub/trivia/file_ops.hpp

@@ -11,14 +11,12 @@ namespace triv {
 
     // Improved libc calls:
     void system( string cmd, bool debug=false );
+    string system_read( string cmd, bool debug=false );
 
     // File names, globbing:
     bool file_exists( const string& fname );
-    void fname_divide( const string& fname, string *fdir,
-                       string *fshort, string *fext);
-    void glob_file_list( const string& pattern,
-                         const string& extension, 
-                         vector<string> *fnames );
+    void fname_divide( const string& fname, string *fdir, string *fshort, string *fext);
+    void glob_file_list( const string& pattern, const string& extension, vector<string> *fnames );
     string wordexp_unique( const string& s );
     string next_tmp_file( const string& path_format );