Why aren't there any man pages for disown or other Ubuntu commands?

disown is a bash built in. So man bash will show ...

disown [-ar] [-h] [jobspec ...]

Without options, remove each jobspec from the table of active jobs. If jobspec is not present, and neither the -a nor the -r option is supplied, the current job is used. If the -h option is given, each jobspec is not removed from the table, but is marked so that SIGHUP is not sent to the job if the shell receives a SIGHUP. If no jobspec is supplied, the -a option means to remove or mark all jobs; the -r option without a job‐ spec argument restricts operation to running jobs. The return value is 0 unless a jobspec does not specify a valid job.

There are plenty more of those. Here is a list.

To list the help type

help disown

or other ubuntu commands?

ALL Ubuntu (linux is more precise) commands have a manual page.

---

ulimit does have a manual page.

ULIMIT(3) Linux Programmer's Manual ULIMIT(3)

NAME ulimit - get and set user limits

SYNOPSIS

  #include <ulimit.h>

  long ulimit(int cmd, long newlimit);

But you probably meant the parameter?

2 ways:

$help ulimit
ulimit: ulimit [-SHabcdefilmnpqrstuvxT] [limit]
    Modify shell resource limits.

    Provides control over the resources available to the shell and processes
    it creates, on systems that allow such control.

    Options:
      -S    use the `soft' resource limit
      -H    use the `hard' resource limit
      -a    all current limits are reported
      -b    the socket buffer size
      -c    the maximum size of core files created

 ...

$ ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 46690
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 46690
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

When you type help you see the commands that are built in bash. To see help for these commands type help <command>:

help ulimit
help disown

When you use man (short for manual), you display help for binary programs that are not part of bash. You noticed that you get the help for ulimit if you type man ulimit. However, the manual for ulimit is not for the bash command. When you type man ulimit you get the manual for the C programming header file ulimit.h, which is something completely different.

ulimit and disown are Bash built in functions and those don't have a manpage of its own but are described in the Bash manpage.

If you are running bash you can use the help command, e.g.:

$ help disown

You may want to pipe the output into less so you can scroll and search, e.g.

$ help disown | less