Revert "Remove shell commands registration (#1064)" (#1073)

This reverts commit 06cc17b6b4.

pwndbg/__init__.py

@@ -44,6 +44,7 @@ import pwndbg.commands.rop
 import pwndbg.commands.ropper
 import pwndbg.commands.search
 import pwndbg.commands.segments
+import pwndbg.commands.shell
 import pwndbg.commands.stack
 import pwndbg.commands.start
 import pwndbg.commands.telescope

pwndbg/commands/shell.py

@@ -0,0 +1,84 @@
+"""
+Wrapper for shell commands.
+"""
+
+import os
+
+import gdb
+
+import pwndbg.commands
+import pwndbg.which
+
+shellcmds = [
+    "asm", # pwntools
+    "awk",
+    "bash",
+    "cat",
+    "chattr",
+    "chmod",
+    "chown",
+    # "clear",
+    "constgrep", # pwntools
+    "cp",
+    "cyclic", # pwntools
+    "date",
+    "diff",
+    "disasm", # pwntools
+    "egrep",
+    # "find", don't expose find as its an internal gdb command
+    "grep",
+    "htop",
+    "id",
+    # "kill",
+    # "killall",
+    "less",
+    # "ln",
+    "ls",
+    "man",
+    "mkdir",
+    "mktemp",
+    "more",
+    "mv",
+    "nano",
+    "nc",
+    "ping",
+    "pkill",
+    "ps",
+    "pstree",
+    "pwd",
+    "pwn", # pwntools
+    "rm",
+    "sed",
+    "sh",
+    "sort",
+    "ssh",
+    "sudo",
+    "tail",
+    "top",
+    "touch",
+    "unhex", # pwntools
+    "uniq",
+    "vi",
+    "vim",
+    "w",
+    "wget",
+    "who",
+    "whoami",
+    "zsh",
+]
+
+shellcmds = filter(pwndbg.which.which, shellcmds)
+
+def register_shell_function(cmd):
+    def handler(*a):
+        if os.fork() == 0:
+            os.execvp(cmd, (cmd,) + a)
+        os.wait()
+
+    handler.__name__ = str(cmd)
+    handler.__doc__ = 'Invokes {}'.format(cmd)
+
+    pwndbg.commands.Command(handler, False)
+
+for cmd in shellcmds:
+    register_shell_function(cmd)