Bash if run a command Post: 302920546

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Top Forums Shell Programming and Scripting Bash if run a command Post 302920546 by cokedude on Friday 10th of October 2014 03:46:58 AM

10-10-2014

Registered User

Quote:

Originally Posted by Don Cragun

I don't understand what you're trying to do. On a system with no active message queues, shared memory segments, or semaphores, the output from ipcs will be something like:

Code:

iIPC status from <running system> as of Thu Oct  9 11:22:09 PDT 2014
T     ID     KEY        MODE       OWNER    GROUP
Message Queues:

T     ID     KEY        MODE       OWNER    GROUP
Shared Memory:

T     ID     KEY        MODE       OWNER    GROUP
Semaphores:

So, the output from:

Code:

ipcs|grep Shared|awk '{print $2}'

will be:

Code:

Memory:

and the condition in your if statement will always evaluate to false.

If, in addition to showing us code that doesn't work, you would also tell us what you're trying to do, we might be better able to help.

And, no. You do not want to enclose a command substitution in backquotes unless you are trying to perform a command substitution on the results of a command substitution.

It looks like we are using two different distros of Linux. Our output is a bit different. I am using Fedora.

Code:

$ ipcs

------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status      
0x00000000 262145     bob        600        393216     2          dest         
0x00000000 2523138    bob        600        393216     2          dest         
0x00000000 2555907    bob        600        393216     2          dest         
0x00000000 3375108    bob        600        998400     2          dest         
0x00000000 3440645    bob        666        40         1                       

------ Semaphore Arrays --------
key        semid      owner      perms      nsems     
0x000005b1 262146     bob        600        6         

------ Message Queues --------
key        msqid      owner      perms      used-bytes   messages

I am working on a C project that spawns threads, creates shared memory, and creates semaphore arrays. It is annoying to have to keep typing or searching my bash history for:

Code:

ipcrm -s $(ipcs | grep bob | awk '{printf "%s ",$2}')
ipcrm  shm $(ipcs | grep bob | awk '{printf "%s ",$2}')

So I was thinking I could do something like this.

Code:

if [ `$(ipcs | grep Shared | awk '{print $2}')` == "Shared"]
ipcrm  shm $(ipcs | grep bob | awk '{printf "%s ",$2}')

I wanna do that first behavior until $2 equals Semaphore.

Code:

if [ `$(ipcs | grep Semaphore | awk '{print $2}')` == "Semaphore"]
ipcrm -s $(ipcs | grep bob | awk '{printf "%s ",$2}'

)

I am not sure how to this. I have been reading the bash documentation for several days with no luck.

cokedude

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