Steve Bourne Talks About the History of Sh

An anonymous reader writes "Steve Bourne, the creator of the Bourne shell, or sh, talks about its history as the default Unix shell of Unix Version 7. Bourne worked on the shell in 1975 and said the process took no more than 6 months. Sh aimed to improve on the Thompson shell. 'I did change the shell so that command scripts could be used as filters. In the original shell this was not really feasible because the standard input for the executing script was the script itself. This change caused quite a disruption to the way people were used to working. I added variables, control flow and command substitution. The case statement allowed strings to be easily matched so that commands could decode their arguments and make decisions based on that. The for loop allowed iteration over a set of strings that were either explicit or by default the arguments that the command was given. I also added an additional quoting mechanism so that you could do variable substitutions within quotes. It was a significant redesign with some of the original flavor of the Thompson shell still there. Also I eliminated goto in favour of flow control primitives like if and for. This was also considered rather radical departure from the existing practice. Command substitution was something else I added because that gives you very general mechanism to do string processing; it allows you to get strings back from commands and use them as the text of the script as if you had typed it directly. I think this was a new idea that I, at least, had not seen in scripting languages, except perhaps LISP,' he says."

Comments

Re:Greenspun's Tenth Rule

[Sir Groane]

Because Steve Bourne was doing this work back in 1975! About that time people had only just got beyond programming by biting holes in paper-tape with their teeth!

These days it is quite easy to get embedded perl or lisp etc.

Yes, PowerShell

[benjymouse]

Available from Microsoft for XP, 2003; included in Server 2008 and Windows 7.

The name is really lame, but it *is* damn powerful. At least for Windows which has most of it API exposed through object-oriented technologies (COM, .NET and WMI) which are easily used in a unified way by PowerShell.

Just a few quick samples:

• List all .exe files in current dir and below: ls -r . *.exe
• Calculate their combined size: ls -r . *.exe | measure -sum Length
• Find the latest version of all .exe files below the current directory: ls -r . *.exe | sort -des LastWriteTime | group Name | %{$_.Group[0]}
• Instead of finding the latest, delete those with a more recent version somewhere: ls -r . *.exe | sort -des LastWriteTime | group Name | %{$_.Group|select -skip 1} | rm
• Read files and directories from current directory out loud through the speakers: $sam=new-object -com SAPI.SPVoice; ls | %{$sam.Speak($_)}
• List processes consuming (the "working set") more than 100MB: ps|?{$_.WS -gt 100MB}
• -Kill them instead: ps|?{$_.WS -gt 100MB}|kill
• Wait for the "import" process to exit: (ps "powershell_ise").WaitForExit()