Question

I have seen the following script:

$ ./crazy-malloc &
[1] 2817
malloced 3056 MB
$ jobs -x pmap %1
2823: ./crazy-malloc
000cc000 4112K rw--- [ anon ]
004d0000 104K r-x-- /lib/ld-2.3.5.so
004ea000 4K r---- /lib/ld-2.3.5.so
004eb000 4K rw--- /lib/ld-2.3.5.so
004ee000 1168K r-x-- /lib/libc-2.3.5.so
00612000 8K r---- /lib/libc-2.3.5.so
00614000 8K rw--- /lib/libc-2.3.5.so
00616000 8K rw--- [ anon ]
006cf000 124388K rw--- [ anon ]
08048000 4K r-x-- /home/john/examples/mm/crazy-malloc
08049000 4K rw--- /home/john/examples/mm/crazy-malloc
08051000 2882516K rw--- [ anon ]
b7f56000 125424K rw--- [ anon ]
bfa43000 84K rw--- [ stack ]
bfa58000 5140K rw--- [ anon ]
ffffe000 4K ----- [ anon ]
total 3142980K

Q1> what is the usage of the line jobs -x pmap %1? What does %1 indicate here?

jobs -x command [ args … ] If the -x option is supplied, jobs
replaces any jobspec found in command or args with the corre-sponding
process group ID, and executes command passing it args, returning its
exit status.

pmap – report memory map of a process

Q2> What the first two columns represent?

Answer 1

1. %1 represents the process which you just started and backgrounded (./crazy-malloc, pid 2817). The command jobs -x pmap %1 expands to pmap 2817.

2. The four columns in the output of pmap represent, respectively, the base address, size, permissions, and mapped file for each memory region mapped by your process.