Can't execute .out files, getting permission denied

command-line executable c++ compiler

93,419

Solution 1

Usually, g++ gives the created file execute permissions. If you do not pass the -o option, the file will be named a.out.

Two possible reasons why your file does not have the execute bit set, with their solutions:

The umask value is set to a value like 0133, thereby preventing the execute bit from being set. Solution: set the permissions explicitly:
```
chmod 755 a.out
```
The filesystem you're working on does not support Linux permissions. This could be the case if you're putting files on a FAT32-formatted flash drive. Solution: either back up the files and format it to ext2 or mount the drive with fmask=0022 or umask=0022 (omitting fmask). See the Mount options for fat section on the manual page of mount for more details.

For bash scripts which do not have the execute bit set, you could run bash file.sh. Such a feature exists for all files with executable content (compiled files and files with a shebang line #!/path/to/interpreter set). To execute files without the execute bit set, use the special file /lib/ld-linux.so.2 (or /lib/ld-linux-x86-64.so.2 for 64-bit applications) to run such a program:

/lib/ld-linux-x86-64.so.2 a.out

Solution 2

.out is an unusual extension. Usually this would normally signify a "trace output" file.

Check your syntax that you are using to compile

e.g.

gcc myfile.c /usr/lib/libsomelibrary.a -o outputfilename

or maybe

g++ myfile.cpp -lm -o outputfilename

You can should examine to see if the executable bit is set on the file

ls -l a.out

or you can just force the executable bit

chmod +x a.out

then you can run your file

./a.out

or simply

a.out

You should also perhaps check that the output file has been written correctly as a binary

i.e.

file a.out

This will report what format the file is - either a script or a binary

You rarely need to execute as root unless you have restricted who should be able to run the executable.

If you have compiled as root (e.g. sudo make), or have a Makefile that installed the executable as root then can I suggest you regain the permission as the user logged in

i.e.

sudo chown fred:fred a.out

i.e. replace "fred" with your user id.

Solution 3

Just copy the folder to your home folder and it will work. You are probably trying to run it on an external drive or something.

93,419

Shamim Hafiz - MSFT

Trying to catch up with and fill in the technological blanks...

Updated on September 18, 2022

Comments

Shamim Hafiz - MSFT over 1 year
I have written a C++ program and complied it to produce a.out file. However, whenever I try to run it, I get Permission Denied. I read that we can use sudo, but I can't quite get it to work. I use something like, sudo "./a.out" but that too doesn't work.

Edit:

Here is the message I get when I try "./a.out".
```
bash: ./a.out: Permission denied
```
- Admin almost 13 years
  
  What is the output of ls -l a.out? What is the output of file a.out? Is the executable on a USB memory stick / Harddisk?
- Admin almost 13 years
  
  Its on Harddisk. Its the same file created soon after the the compilation process. I didn't set any other parameters.
- Admin almost 13 years
  
  -rw------- 1 shamimhafiz shamimhafiz 7721 2011-05-22 23:30 a.out Is the output of ls -l a.out
- Admin almost 13 years
  
  So based on the output of ls -l a.out it's a permissions problem. If you do chmod +x a.out then try ./a.out does it execute? What is the output of umask?
- Admin almost 13 years
  
  @JRT: It doesn't execute. Doing "chmod +x a.out" doesn't give any message, but looks like it has no effect. Trying "ls -l a.out" again still shows the same thing.
Shamim Hafiz - MSFT almost 13 years

Thanks for the information. I am actually logged in as the only user, and I presume I am the main user. I am not quite sure, why I need to use administrative authentication anyway. How would I be able to remove this option so I can always run the files.
SpamapS almost 13 years

a.out is a legacy feature of the compiler so it produces a predictable filename if you didn't ask for one. This is not a permissions problem, but a misunderstanding of how compilers and C++ work.
JRT almost 13 years

Linux/Unix does not rely on file extensions to determine the file-type. Normally executable files have no extension at all. Also, the format to executable a file does not differ between shells generally. All shells should work find with ./a.out unless it is some exotic shell.
JRT almost 13 years

If he had no main function, it would not link and therefore it would not produce an a.out file.
hometoast almost 13 years

I'd bet it's as simple as fixing the executable bit like you said: chmod +x a.out.
Shamim Hafiz - MSFT almost 13 years

I tried "chmod +x a.out" but no luck. I have updated my question to include the error message.
Shamim Hafiz - MSFT almost 13 years

Even trying "sudo chown fred:fred a.out" with proper name brought no luck.
nilsonneto almost 13 years

Gunner - please copy and paste the complete output in the terminal starting with your compile command, followed by the ls -l, chmod +x and finally the execution. Please confirm your name by typing "whoami"
Shamim Hafiz - MSFT almost 13 years

This answer is more interesting, just to add, the way I Installed Ubuntu is over Windows and a folder named was created on C drive(windows installation drive). This drive is formatted as FAT32. Could this have something to do with that?
Lekensteyn almost 13 years

You've done a Wubi installation (C:\Ubuntu had been created). This should not be a problem unless you're putting files on "C:" and not your Ubuntu installation. If you're not using Windows, or have plenty of disk space, I suggest installing Ubuntu on a dedicated partition. And again, NTFS / FAT32 does NOT support Linux permissions, so you can run sudo chown user file, chmod 755 file, it won't work. You really need an EXT filesystem for that.
Shamim Hafiz - MSFT almost 13 years

Actually I am saving the file on D drive, which I access through media/DOCS/workfolder. This work folder along with all other D drive folders are visible inside media/DOCs. Could this be the reason?
Lekensteyn almost 13 years

The same story, none of Windows filesystems supports Linux file permissions. You should put the files on a filesystem formatted EXT.
Shamim Hafiz - MSFT almost 13 years

So simply working on a folder that belongs to Ubuntu should do the trick, right? I mean, I should not use folders that are not part of Ubuntus File System Structure?
Lekensteyn almost 13 years

Exactly, just stay in ~, I create ~/projects and put all my projects in it, you could do the same thing.
Aaron John Sabu about 4 years

Mine was the second case. I haven't tried it out on ext4 but at least I know what's wrong! :D
Mohamad Fakih about 4 years

"just copy the folder to your home folder and it will work" this worked for me. Thanks. Though it seems weird as the file is exectuable.