> What is the difference between: > cd dir; do_smth cd into dir then run do_smth; if 'cd dir' fails, then run do_smth anyway
> and > cd dir && do_smth cd into dir then run do_smth; if 'cd dir' fails then don't run do_smth It's a logic control statement meaning AND so cmd1 AND cmd1 is evaluated by the shell for 'truth'. If the first statement is false (i.e. cmd1 fails), then this short-circuits the logic as the shell doesn't need to know the truth/falsehood of the second 'statement' (cmd2), so it doesn't evaluate it. So 'a && b' is equivalent to 'if a then b'. || (or) has similar uses. See the man page for the shell you are using for more details, e.g. 'man ksh' on my system has some info about this idiom. HTH, David Carter-Hitchin. -- Royal Bank of Scotland Interest Rate Derivatives IT 135 Bishopsgate LONDON EC2M 3TP Tel: +44 (0) 207 085 1088 *********************************************************************************** The Royal Bank of Scotland plc. Registered in Scotland No 90312. Registered Office: 36 St Andrew Square, Edinburgh EH2 2YB. Authorized and regulated by the Financial Services Authority This e-mail message is confidential and for use by the addressee only. If the message is received by anyone other than the addressee, please return the message to the sender by replying to it and then delete the message from your computer. Internet e-mails are not necessarily secure. The Royal Bank of Scotland plc does not accept responsibility for changes made to this message after it was sent. Whilst all reasonable care has been taken to avoid the transmission of viruses, it is the responsibility of the recipient to ensure that the onward transmission, opening or use of this message and any attachments will not adversely affect its systems or data. No responsibility is accepted by The Royal Bank of Scotland plc in this regard and the recipient should carry out such virus and other checks as it considers appropriate. Visit our websites at: http://www.rbos.com http://www.rbsmarkets.com ******************************************************************************** _______________________________________________ Help-make mailing list [email protected] http://lists.gnu.org/mailman/listinfo/help-make
