Cd Post: 7977

Sponsored Content

Top Forums UNIX for Dummies Questions & Answers Cd Post 7977 by Perderabo on Thursday 4th of October 2001 09:37:55 AM

10-04-2001

Administrator Emeritus

Quote:

Originally posted by Neo

/usr/bin/cd /tmp; rm -rf *

This would appear, if I'm not mistaken, to spawn a child process that would remove all the files in the /tmp directory.

Sorry, that won't work. I sure hope nobody tried that. Try this instead:
/usr/bin/cd /tmp; /usr/bin/pwd

Even when commands are stacked with semicolons, we still have a shell processing the command line. And it still must spawn a child, let the child run /usr/bin/cd, wait for the child to die, spawn a second child, which will run /usr/bin/pwd.

Quote:

Originally posted by devnul
Well, I just wanted to add that on Solaris /usr/bin/cd is a two-line shell script....

cmd=`basename $0`
$cmd "$@"
That's it.. Nothing more...

Actually there are some comments as well which date it Feb 6, 1995 and it has a 1995 copyright. This gives us some idea of when it appeared. 1995 does sound about right.

HP's version is also a simple script:
cd $@
exit $?

HP doesn't show a date, but it does have a comment showing that it is revision 72.2. It's hard to imagine 72 revisions on a script like this, but I guess it's not a job you assign to your best programmer.

The format of Sun's script shows that it's using its name to find the command. I got a list of all the files in /usr/bin linked to the same file. The list is alias, bg, cd, command, fc, fg, getopts, hash, jobs, kill, read, test, type, ulimit, umask, unalias, and wait. Only kill and test really make any sense. Oh well.

Perderabo

View Public Profile for Perderabo

Find all posts by Perderabo

LEARN ABOUT OPENSOLARIS

shells

shells(4)							   File Formats 							 shells(4)

NAME

       shells - shell database

SYNOPSIS

       /etc/shells

DESCRIPTION

       The shells file contains a list of the shells on the system. Applications use this file to determine whether a shell is valid. See getuser-
       shell(3C). For each shell a single line should be present, consisting of the shell's path, relative to root.

       A hash mark (#) indicates the beginning of a comment; subsequent characters up to the end of the line are not interpreted by  the  routines
       which search the file. Blank lines are also ignored.

       The following default shells are used by utilities: /bin/bash, /bin/csh, /bin/jsh, /bin/ksh, /bin/ksh93, /bin/pfcsh, /bin/pfksh, /bin/pfsh,
       /bin/sh, /bin/tcsh, /bin/zsh, /sbin/jsh, /sbin/sh, /usr/bin/bash, /usr/bin/csh, /usr/bin/jsh, /usr/bin/ksh, /usr/bin/ksh93, /usr/bin/pfcsh,
       /usr/bin/pfksh, /usr/bin/pfsh, and /usr/bin/sh, /usr/bin/tcsh, /usr/bin/zsh, and /usr/sfw/bin/zsh. /etc/shells overrides the default list.

       Invalid shells in /etc/shells could cause unexpected behavior, such as being unable to log in by way of ftp(1).

FILES

       /etc/shells    list of shells on system

SEE ALSO

       vipw(1B), ftpd(1M), sendmail(1M), getusershell(3C), aliases(4)

SunOS 5.11							    20 Nov 2007 							 shells(4)