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bin/bash and bin/sh

hai
what is the difference between bin/bash and bin/sh

bin/sh was the old "original" shell, it's left for nostalgic compatibility but is usually symlinked to bin/bash unless the sysadmin has another shell preference.

TenTenths is correct regarding the symlinking of sh to bash. My understanding is that when you put #/bin/sh at the top your your scripts though, bash will operate in Bourne Shell and perhaps lose some Bash features as stated in The Linux Documentation Project's Advanced Shell Scripting guide:

"Using #!/bin/sh, the default Bourne shell in most commercial variants of UNIX, makes the script portable to non-Linux machines, though you sacrifice Bash-specific features. The script will, however, conform to the POSIX [5] sh standard."

http://tldp.org/LDP/abs/html/sha-bang.html

This from the bash manual page:

Code:

If bash is invoked with the name sh, it  tries  to  mimic  the  startup

      behavior  of  historical  versions  of sh as closely as possible, while

      conforming to the POSIX standard as well.  When invoked as an  interac‐

      tive  login  shell, or a non-interactive shell with the --login option,

      it first attempts to read and execute commands  from  /etc/profile  and

      ~/.profile,  in  that  order.  The  --noprofile  option may be used to

      inhibit this behavior.  When invoked as an interactive shell  with  the

      name  sh,  bash  looks for the variable ENV, expands its value if it is

      defined, and uses the expanded value as the name of a file to read  and

      execute.  Since a shell invoked as sh does not attempt to read and exe‐

      cute commands from any other startup files, the --rcfile option has  no

      effect.  A  non-interactive  shell  invoked  with the name sh does not

      attempt to read any other startup files.  When  invoked  as  sh,  bash

      enters posix mode after the startup files are read.