Which files in `/proc` provides the following information?

Question

From https://unix.stackexchange.com/a/492346/674

Kernels such as Linux and the kernels of the BSDs provide four (relevant) pieces of information about a process, via files in /proc and sysctl():

• its program image short name, a.k.a. the short name used for process accounting;
• its argument strings, initialized by execve() and modifiable at runtime;
• its environment strings, initialized by execve() and modifiable at runtime; and
• the full pathname of its executable program image file.

Which file in /proc (and which arguments to sysctl()) provide each of the four pieces of information? Thanks.

Answer 1

On Linux:

• its program image short name, a.k.a. the short name used for process accounting;

/proc/<pid>/comm

• its argument strings, initialized by execve() and modifiable at runtime;

/proc/<pid>/cmdline

• its environment strings, initialized by execve() and modifiable at runtime; and

/proc/<pid>/environ

• the full pathname of its executable program image file.

/proc/<pid>/exe

(which is a symbolic link to the file).

Additional technical detail for these files can be found in man 5 proc.

On FreeBSD:

• its program image short name, a.k.a. the short name used for process accounting;

• sysctl() with CTL_KERN, KERN_PROC, and KERN_PROC_ALL/KERN_PROC_PROC OIDs.
• Dumpable with sysctl -x kern.proc.all
• One of the fields in /proc/PID/status.
• (if compatibility is installed) one of the fields in /compat/linux/proc/PID/status.

• its argument strings, initialized by execve() and modifiable at runtime;

• sysctl() with CTL_KERN, KERN_PROC, and KERN_PROC_ARGS OIDs.
• Also /proc/PID/cmdline.
• (if compatibility is installed) /compat/linux/proc/PID/cmdline.

• its environment strings, initialized by execve() and modifiable at runtime; and

• sysctl() with CTL_KERN, KERN_PROC, and KERN_PROC_ENV OIDs.
• (if compatibility is installed) /compat/linux/proc/PID/environ.

• the full pathname of its executable program image file.

• /proc/PID/file (which is a symbolic link to the file).
• (if compatibility is installed) /compat/linux/proc/PID/exe.