How to store the output of a gdb command into a variable?

Question

I'm trying to store the output of a gdb command into a gdb variable. I'm following the instruction from here. But when I print the variable it shows empty.

My pop_stack file contains this

20
268435372

I use the following command to store the value 268435372 from the pop_stack into gdb variable $pop_ele. And try to print the value as hexadecimal. But the $pop_ele shows empty.

(gdb) shell echo set \$pop_ele=\"$(tail -n 1 pop_stack)\"
(gdb) p/x $pop_ele

output:

set $pop_ele="268435372"
$8 = 0x0

My desire output for p/x $pop_ele command is 0xfffffac

Please help.

This question is similar to: Redirecting/storing output of shell into GDB variable?. If you believe it’s different, please edit the question, make it clear how it’s different and/or how the answers on that question are not helpful for your problem. — user202729
– user202729, Commented Oct 25, 2024 at 2:47

dash-o · Accepted Answer · 2020-01-25 05:52:57Z

1

With gdb 8.X, possible to use shell and source to execute commands that depends on external data.

shell echo set \$pop_ele=$(tail -n1 pop_stack) > gdb.tmp
source gdb.tmp

answered Jan 25, 2020 at 5:52

dash-o

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