bash

fereshteh · 09-15-2013, 01:37 AM

hi all
i have seen one command line in my program's build.bash file. It is:
[code]if [ -n "${USE_PARALLEL_IO:+1}" ] && [ -n "${USE_MPI:+1}" ]; then if [ "${which_MPI}" = "mpich" ]; then ...
i want to know what is the meaning of && sign .
All the best
fereshte

jdkaye · 09-15-2013, 01:48 AM

It marks an "and list" So

Code:

command1 && command2

means "execute command1 and then execute command2".
Example:

Code:

sudo aptitude update && sudo aptitude safe-upgrade

You can find all this and more in your favourite (and free) bash manual.
Enjoy
jdk

colucix · 09-15-2013, 01:53 AM

Please take a look at the bash manual here: http://www.gnu.org/software/bash/man...ref.html#Lists
In your if/then construct, you can think at && as logical AND, that means the condition is true if both the expressions inside square brackets are true.

fereshteh · 09-15-2013, 02:44 AM

dear
many thanks for your reply and sending required link
cheers
fereshte