I have written a simple helloworld.c program. I can compile it and run it on linux terminal using gcc and ./a.out command. My query is regarding calling .o file without any extension. For example, to run my program instead of typing "./helloworld.out", I want to run it using keyword "helloworld" on my terminal. Any hints???
Thank You.
Just compile using
gcc -o helloworld helloworld.c
The -o option is for the output file name
Then use:
./helloworld
You need the ./ to tell the shell where the executable resides, since the current directory is unlikely to be in $PATH.
Related
When i type the command gcc filename.c a new file 'a.exe' is created, then i have to run a.exe to get my program to run.
Is there a way just to type one command to run my program or can you run a C program without having a new .exe file being created?
I use gcc version gcc (MinGW.org GCC-6.3.0-1) 6.3.0
(Complete beginner with C)
You can't run the .c file directly - you have to compile it into an executable (using gcc or whatever compiler). However, you don't have to compile it every time you want to run it - you only have to compile it after first creating it and after you make any changes. So you can run gcc once, then run a.exe multiple times.
You can name the executable something other than a.exe if you wish using the -o option:
gcc -o prog filename.c
./prog
You could make a .bat file that does everything for you. For example:
build.bat
gcc %1.c -o %1.exe
%1.exe
This will build and run the file for you:
build hello
will compile and run hello.exe for you.
This question already has answers here:
Why do some compilers use "a.out" as the default name for executables?
(2 answers)
Closed 6 years ago.
I am learning C in Linux Mint, so I made a directory in which I place my programs. Whenever I compile a program, everytime a.out is being over-written with the new compiled program.
For ex. To compile a hello.c file I run command: cc hello.c, Now this program will create a.out, but I want it to be hello.out
Why is it?
How can I compile so that hello.c should create hello.out file?
Why only a.out is being created everytime when I make different programs in directory?
Because that's the default behavior of your compiler.
How can I compile so that hello.c should create hello.out file?
In general, refer to the documentation for the compiler you're using, which will tell you how to do this.
Assuming you're using gcc or similar, it's the -o option:
gcc hello.c -o hello.out
Default execution in Unix/Linux is a.out file. If you create your own executable then compile program like:
cc hello.c -o hello.out
./hello.out // manually created executable file
or
cc hello.c -o hello
./hello // manually created executable file
Unix/Linux doesn't care about extensions. -o hello basically your suggested name for the executable file that gcc would create.
Why every time a.out is created?
a.out remains the default output file name for executables created by certain compilers/linkers when no output name is specified, even though these executables are no longer in the a.out format.
Please see the wiki page of a.out.
Share your compilation command.
In the compilation command you can mention what the name of the output binary file, like: "gcc hello.c -o hello" then the binary file name will be (hello) because you mention after flag "-o" that you want to name the output file by the name "hello".
If you don't add the flag "-o" with a name, then the default name for the binary file is "a.out".
I am new to C. Here is my "Hello, World!" program.
#include <stdio.h>
int main(void)
{
printf("Hello, World!\n");
return 0;
}
After I try to run it using Terminal it says:
/Users/macbook/Desktop/peng/Untitled1
-bash: /Users/macbook/Desktop/peng/Untitled1: Permission denied
Why?
First save your program as program.c.
Now you need the compiler, so you need to go to App Store and install Xcode which is Apple's compiler and development tools. How can you find App Store? Do a "Spotlight Search" by typing ⌘Space and start typing App Store and hit Enter when it guesses correctly.
App Store looks like this:
Xcode looks like this on App Store:
Then you need to install the command-line tools in Terminal. How can you start Terminal? You need to do another "Spotlight Search", which means you type ⌘Space and start typing Terminal and hit Enter when it guesses Terminal.
Now install the command-line tools like this:
xcode-select --install
Then you can compile your code with by simply running gcc as in the next line without having to fire up the big, ugly software development GUI called Xcode:
gcc -Wall -o program program.c
Note: On newer versions of OS X, you would use clang instead of gcc, like this:
clang program.c -o program
Then you can run it with:
./program
Hello, World!
If your program is C++, you'll probably want to use one of these commands:
clang++ -o program program.cpp
g++ -std=c++11 -o program program.cpp
g++-7 -std=c++11 -o program program.cpp
First make sure you correct your program:
#include <stdio.h>
int main(void) {
printf("Hello, World!\n"); //printf instead of pintf
return 0;
}
Save the file as HelloWorld.c and type in the terminal:
gcc -o HelloWorld HelloWorld.c
Afterwards, just run the executable like this:
./HelloWorld
You should be seeing Hello, World!
A "C-program" is not supposed to be run. It is meant to be compiled into an "executable" program which then can be run from your terminal. You need a compiler for that.
Oh, and the answer to your last question ("Why?") is that the file you are trying to execute doesn't have the executable rights set (which a compiler usually does automatically with the binary, which let's infer that you were trying to run the source code as a script, hence the hint at compiling.)
This is Working in 2019
By default, you can compile your name.c using the terminal:
cc name.c
And if you need to run, just write
./name.out
To do this:
Open the terminal
Type in the terminal: nano ; which is a text editor available for the terminal. When you do this, something like this would appear.
Here you can type in your C program
Type in Ctrl + X → which means to exit.
save the file by typing in Y to save the file
Type the file name; e.g., helloStack.c (don't forget to add .c)
When this appears, type in gcc helloStack.c
And then ./a.out: this should give you your result!
For compiling a C program on your latest macOS, just type the following in the terminal after saving the file with a .c extension and on reaching the path where the file is saved:
cc yourfilename.c
Once you have checked all the errors after compilation (if any), type the following for executing the code:
./a.out
These commands are tested on macOS v10.14 (Mojave) and are working perfectly fine.
To compile a C program in macOS, simply follow the below steps
Using the cd command in terminal, go to your C program location and then type the command present below:
make filename
then type
./filename
The answer is chmod 755 hello - it makes the file executable... I had same problem on macOS, which is now solved.
nano hello.c
make hello
chmod 755 hello
Then you run it by ./hello
clang --version
Output:
Apple LLVM version 8.0.0 (clang-800.0.42.1)
Target: x86_64-apple-darwin15.6.0
Nothing was installed. nano make (clang) chmod - all inside macOS already.
On Mac, GCC (executable gcc) is installed by default in /usr/local/bin.
To run C:
gcc -o tutor tutor.c
First you need to install a GCC compiler for Mac (google it and install it from the Internet)
Remember the path where you are storing the C file
Go to Terminal and set the path
E.g., if you have saved in a new folder ProgramC in the Document folder.
Then type this in Terminal:
cd Document
cd ProgramC
Now you can see that you are in folder where you have saved your C program (let you saved your program as Hello.c)
Now compile your program
make Hello
./hello
Recently, I found a program that is kind of a mix between an IDE and a text editor. It supports the syntax of the language and it does formatting, but it does not build and run the program for you. I am running Mac OS X 10.6.8. I looked up how to build C code using the Terminal application. The format is:
gcc [file]
Pretty simple. The problem is that I cannot change the directory of where the built file is outputted, nor can I change the name. By default, every file compiled is outputted in the home directory by the name of 'a.out.' How can I specify the output directory and name?
Thanks!
gcc has a -o option to change the output name. You can specify the path there. E.g.:
$ ls
program.c
$ gcc program.c -o program
$ ls
program program.c
$ mkdir bin
$ gcc program.c -o bin/program
$ ls bin
program
$
You should probably also want to know about a few other common options:
-std=c99, -std=gnu99: Use the c99 standard / with gnu extensions.
-Wall, -Wextra, -pedantic: Enable extra warnings.
-O0 -ggdb: Compile with debugging symbols. Look up how to use gdb.
-O2: Compile with processor-independent optimizations. Not compatible with -O0.
How can I execute a.exe using the Cygwin shell?
I created a C file in Eclipse on Windows and then used Cygwin to navigate to the directory. I called gcc on the C source file and a.exe was produced. I would like to run a.exe.
./a.exe at the prompt
you should just be able to call it by typing in the file name. You may have to call ./a.exe as the current directory is usually not on the path for security reasons.
just type ./a in the shell
To execute a file in the current directory, the syntax to use is: ./foo
As mentioned by allain, ./a.exe is the correct way to execute a.exe in the working directory using Cygwin.
Note: You may wish to use the -o parameter to cc to specify your own output filename. An example of this would be: cc helloworld.c -o helloworld.exe.
Thomas wrote:
Apparently, gcc doesn't behave like the one described in The C Programming language
It does in general. For your program to run on Windows it needs to end in .exe, "the C Programming language" was not written with Windows programmers in mind. As you've seen, cygwin emulates many, but not all, features of a POSIX environment.
gcc under cygwin does not generate a Linux executable output file of type " ELF 32-bit LSB executable," but it generates a windows executable of type "PE32 executable for MS Windows" which has a dependency on cygwin1.dll, so it needs to be run under cygwin shell. If u need to run it under dos prompt independently, they cygwin1.dll needs to be in your Windows PATH.
-AD.
Apparently, gcc doesn't behave like the one described in The C Programming language, where it says that the command cc helloworld.c produces a file called a.out which can be run by typing a.out on the prompt.
A Unix hasn't behaved in that way by default (so you can just write the executable name without ./ at the front) in a long time. It's called a.exe, because else Windows won't execute it, as it gets file types from the extension.
Just call it
> a
Make sure it will be found (path).
When you start in Cygwin you are in the "/home/Administrator" zone, so put your a.exe file there.
Then at the prompt run:
cd a.exe
It will be read in by Cygwin and you will be asked to install it.