I am an Ubuntu user. What is the difference between g++ file.cpp -o file and g++ -c file.cpp?
I know that g++ -c file.cpp creates an object file, file.o.
But what about g++ file.cpp -o file?
I have been using this command for a long time, but I don't know the file generated as an output (it is just "file").
I have to run ./file to execute the file.
With -o you can specify the output file name.
In your, e.g., g++ file.cpp -o file means: compile file.cpp to file.
Without -o your source code will compile to a.out file.
If you worry about others option in g++, you can always use g++ --help. It will show you all parameters and their meanings. For example, -o meaning from help:
-o <file> : Place the output into <file>
g++ file.cpp -o file produces an executable file (which normally have no extensions on Linux). -o specifies the output file name. If you do just g++ file.cpp, the file will be named a.out.
It's equivalent to g++ -c file.cpp followed by g++ file.o -o file, except that the file.o is not saved anywhere.
Note that you can use -o <filename> with -c as well, to change the name of the object file.
-o simply means "output" and allows you to choose your output file's name. It remains totally allowed to specify both -c and -o if you need it.
Simply, cc used to name a final, linked executable a.out for historical reasons and will still keep on doing it for while, when using -c is primarily meant to compile multiple parts before assembling from the beginning, thus preserving the original name.
That's why see more often -o specified when compiling final executable than other types of compiled files.
-cand-ooptions are covered in "Options Controlling the Kind of Output".-Eoption; Or to stop and generate only assembly output with the-Soption; Or to stop after creating an object file with the-coption.