When you are running a command hit Control-T anytime, its very useful when a command looks stuck.
It causes the kernel to spit out a line similar to the following:
load: 0.69 cmd: awk 56538 [piperd] 0.96r 0.00u 0.00s 0% 2380k
Shows load 1m load-average (“load: 0.69”), the ucomm (utility basename) of the running process (“awk”), the process ID (PID) of the running process (56538), the wait channel or wchan status (“piperd” for pipe read), the real number of seconds the command has been running thus far (“0.96r”), the user seconds (“0.00u”), system seconds (“0.00s”), CPU utilization (0%) and rss or resident set memory size (“2380k”)
That line comes from the kernel and not a sub-process, userland process, nor forked process
When you get more than just the “load: …” line out of a Ctrl-T, for example… “sleep: about 99 second(s) left out of the original 100”
The extra information comes from the running process itself responding to a SIGINFO that was generated by the kernel and sent to said running process (following the initial strike of Ctrl-T and printing of “load: …” line)
Ctrl-T does not and cannot interfere with a running program