fix the issue of check_file_writable for some Linux systems

https://github.com/OpenGene/fastp/issues/50wq

Author: sfchen

src/options.cpp

@@ -50,13 +50,13 @@ bool Options::validate() {
     }
 
     if(!out1.empty()) {
-        //check_file_writable(out1);
+        check_file_writable(out1);
         if(out1 == out2) {
             error_exit("read1 output (--out1) and read1 output (--out2) should be different");
         }
     }
     if(!out2.empty()) {
-        //check_file_writable(out2);
+        check_file_writable(out2);
     }
 
     if(compression < 1 || compression > 9)
@@ -179,4 +179,4 @@ bool Options::validate() {
         error_exit("overrepresentation_sampling should be 1~10000");
 
     return true;
-}
+}

src/util.h

@@ -186,13 +186,13 @@ inline void check_file_valid(const  string& s) {
 }
 
 inline void check_file_writable(const  string& s) {
-    if(is_directory(s)){
-        cerr << "ERROR: '" << s << "' is a folder, not a file, quit now" << endl;
+    string dir = dirname(s);
+    if(!file_exists(dir)) {
+        cerr << "ERROR: '" << dir << " doesn't exist. Create this folder and run this command again." << endl;
         exit(-1);
     }
-    string dir = dirname(s);
-    if(!is_directory(dir)){
-        cerr << "ERROR: '" << s << "' cannot be created, please confirm the folder "<< dir << " exists. Create this folder and run this command again." << endl;
+    if(is_directory(s)){
+        cerr << "ERROR: '" << s << "' is not a writable file, quit now" << endl;
         exit(-1);
     }
 }