Debug using gdb where the program takes input from another program

Question

I need to debug a program that feeds on the output of another program. Hence, writing the output of the 'feeder' into a file, and piping that to the 'reader' doesn't work.

Normal run:

# feeder | ./reader

This is NOT an option here:

# feeder > data
# gdb ./reader
(gdb) run < data

Because the output of feeder is not continuous. A dump to file, pipe from file would simply push all data at once. — Bgs
– Bgs, Commented Nov 30, 2017 at 0:44

Employed Russian · Accepted Answer · 2017-11-30 01:35:50Z

2

You can make the reader pause and wait for GDB to attach, as described here.

Then run:

feeder | ./reader

in one terminal, and gdb -p $(pgrep reader) in another terminal.

Once gdb is attached, let the reader proceed, and debug it normally.

Update:

Now that you've clarified your constraint, another way is to use named pipe:

mknod /tmp/.pipe p
feeder > /tmp/.pipe
gdb reader
(gdb) run < /tmp/.pipe

edited Nov 30, 2017 at 1:35

answered Nov 29, 2017 at 0:09

Employed Russian

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2 Comments

Bgs Over a year ago

Not the most elegant way, but a well placed sleep could work indeed.

Employed Russian Over a year ago

@Bgs I think your question is under-specified, but you may be able to use a named pipe. Answer updated.

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