Ubuntu – How to overcome “Permission denied” running C program even after “chmod +x”

cchmodcompilingexecutablepermissions

After compiling a C program on Ubuntu 10.10, after executing chmod +x ./a.out, I am still getting bash: ./a.out: Permission denied. How can I run my new executable?

Best Answer

One possible reason is that you are compiling on a file system that has been mounted with the noexec option.

Run mount -l to see the options that file systems are mounted with.

Related Solutions

Ubuntu – Can’t execute .out files, getting permission denied

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

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Ubuntu – Can’t execute .out files, getting permission denied

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