topic Re: Internal commands in Operating System - HP-UX

Internal commands

Shahul — Tue, 29 Jul 2003 07:34:58 GMT

Hi all,

Is there anything called internal commands in HP Unix? I have renamed /usr/bin/ls to ls.old, still ls is listiing the directory. Where from this ls is getting executed?

TIA
Shahul

Re: Internal commands

melvyn burnard — Tue, 29 Jul 2003 07:39:24 GMT

Yes there are certain commands built-in to the shell, but cannot remember too many of them ;-}
If you wish to check where you are sourcing a command, you can always do:
whence
for example
root @uksd3 #whence date
/usr/bin/date

I do know cd is one of hte built-ins, and here is an example
root @uksd3 #whence cd
cd

Re: Internal commands

Sunil Sharma_1 — Tue, 29 Jul 2003 07:46:15 GMT

Hi,
there is lots of Internal Commands in Unix whihc is part of shell basically.
like cd
ls is external command you can find out which ls is getting excuted using which command
#which ls

you will get answer.....

sunil

Re: Internal commands

RAC_1 — Tue, 29 Jul 2003 07:49:12 GMT

Some commands are built into shell. These are called internal.

Check as follows.

whence ls
type ls(type is a internal command in ksh)
which ls

Re: Internal commands

Shahul — Tue, 29 Jul 2003 08:39:30 GMT

Hi,

which ls is giving /usr/bin/ls output. Even if I rename this, ls command works. Don't know where from this?

Thanks and regards
Shahul

Re: Internal commands

Massimo Bianchi — Tue, 29 Jul 2003 08:41:10 GMT

Hi,
i know to be a bit late...

From man csh you get a full list of the built-in commands.

From man ksh you don't get the list, they are talked about here and there.

Massimo

Re: Internal commands

Pete Randall — Tue, 29 Jul 2003 09:08:41 GMT

Shahul,

Most likely you're picking up /sbin/ls.

Pete

Re: Internal commands

melvyn burnard — Tue, 29 Jul 2003 09:28:22 GMT

I believe Pete is correct, as a whence ls on my box does give this as the path, but which ls still shows /usr/bin/ls
There is also no man page for whence, so I suspect/believe that whence is one of htose built-in commands that I had forgotten ;-]
Interestingly, if you start a ksh, and then do a whence ls, this DOES show /usr/bin/ls

Re: Internal commands

Radhakrishnan Venkatara — Tue, 29 Jul 2003 09:57:44 GMT

shahul,

it does take from /sbin/ls.

internal commands are varies according to the shells.

here are some.it may not be same in all shells and in all unix flavours.

: (colon) exec shift
. (dot) exit times
break export trap
continue readonly wait
eval return

how are u ?

radhakrishnan

Re: Internal commands

Sunil Sharma_1 — Tue, 29 Jul 2003 10:25:02 GMT

Hi,

if output of "which ls" /usr/bin/ls
it means in /usr/bin directory ls is there
just check it once again.
and just post the output of
whereis ls

command

Sunil

Re: Internal commands

Bill Hassell — Tue, 29 Jul 2003 11:03:36 GMT

The commands 'which' and 'whereis' are not useful in determining where a command will be found. The shell has many builtin's, namely cd and ls. which and whereis do NOT follow the same rules in looking for something to execute as the shell uses. And it is important to know that there MAY be slightly different beavior between the external command and a shell built-in. As mentioned, whence is the command to use but the best command is 'type' (an alias to whence -v, so use this: type type). ALWAYS use 'type' to determine what will happen when you type a particular string of characters. which and whereis know nothing about shell builtins and aliases. Try these:

type ls
type cd
type pwd
type fc
type for

For instance, which and whereis have no idea what 'for' might be, but 'type' (whence -v) definitely knows. Many shell built-in commands are found in /usr/bin but are simple shell scripts with the shell built-in:

cat /usr/bin/ulimit
type ulimit

There are also situations where the external command is better than the shell built-in:

cd /usr/spool/lp
pwd
/usr/bin/pwd

You'll see that the built-in pwd remembers how you got to the /usr/spool/lp (the legacy directory for the spooler, which is a symlink) but /usr/bin/pwd shows the 'real' directory (/var/spool/lp).

The 'whence' (and 'type') commands are part of POSIX shells such as /usr/bin/sh and /usr/bin/ksh (and bash if you added that shell).

Re: Internal commands

Jerome Baron — Tue, 29 Jul 2003 11:09:57 GMT

ls is in different directory :
/bin
/sbin
/usr/bin

Regards,
Jerome

Re: Internal commands

Rory R Hammond — Wed, 30 Jul 2003 14:50:48 GMT

The commands we execute are deteremed by PATHS. Listed is a copy of my
wh command. which is also linked as whall in my user local bin.

#!/bin/sh
#ident "@(#) Rory Hammond - - /usr/local/bin/wh"
# 07-11-93 replaced C program with this shell
#
# wh
#
# Examine the path for a command & tell which dir has it. Stop with
# the 1st dir that has it.
#
# whall link whall to wh and it will find all occurance in the paths
#

if [ $# -eq 0 ]
then
echo "usage:\t$0 prognam ...." | sed -e 's/\/\//\//g'
exit 1
fi

dirs=`echo $PATH |
sed -e 's/^:/.:/' -e 's/:$/:./' -e 's/::/:.:/' -e 's/:/ /g'`

notfound=

for ffile in $*
do
found=0

for dir in $dirs
do
if [ -x ${dir}/${ffile} -a ! -d "${dir}/$1" ]
then
echo "${dir}/${ffile}"| sed -e 's/\/\//\//g'
found=1
if [ $0 = "whall" ]
then
break
fi
fi
done

if [ ${found} -eq 0 ]
then
notfound="${notfound} $1"
fi

shift
done

#report the not found

for arg in $notfound
do
echo "${arg} not found"
done

exit 0

Re: Internal commands

Hai Nguyen_1 — Wed, 30 Jul 2003 15:00:29 GMT

Shahul,

You might have picked up /sbin/ls.

# whereis ls

shows the paths of ls.

Removing sbin from the path will stop ls from working in your case.

Hai

Re: Internal commands

Rory R Hammond — Wed, 30 Jul 2003 16:55:32 GMT

I am very sorry, posted the incorrect source to wh.

Whereis shows all occurance. The shell script shows which one you are executing

The man pages do describe commands. One of the problems that you encounter alias will fool you path

alias ls="/sbin/ls -l"

man sh-bourne lists the "special commands"

rory

#!/bin/sh
#ident "@(#) Rory Hammond -menlo - /usr/local/bin/wh"
# 07-11-93 replaced C program with this shell
#
# wh
#
# Examine the path for a command & tell which dir has it. Stop with
# the 1st dir that has it.
#
#

if [ $# -eq 0 ]
then
echo "usage:\t$0 prognam ...." | sed -e 's/\/\//\//g'
exit 1
fi

dirs=`echo $PATH |
sed -e 's/^:/.:/' -e 's/:$/:./' -e 's/::/:.:/' -e 's/:/ /g'`

notfound=

for ffile in $*
do
found=0

for dir in $dirs
do
if [ -x ${dir}/${ffile} -a ! -d "${dir}/$1" ]
then
echo "${dir}/${ffile}"| sed -e 's/\/\//\//g'
found=1
break
fi
done

if [ ${found} -eq 0 ]
then
notfound="${notfound} $1"
fi

shift
done

#report the not found

for arg in $notfound
do
echo "${arg} not found"
done

Re: Internal commands

John Meissner — Wed, 30 Jul 2003 17:27:23 GMT

if... as an example you were executing "ls" as many people are using....

type ls

this will show you where the ls command was executed from.

if you are concerned that it might be an aliased command try this

alias

this will show you a list of all aliases you have assigned.