Question

Is there an option for the Linux top command where I can filter processes by name and write the CPU usage of that process every second to a log file?

Answer 1

top & pgrep

To filter the output of top by process name, you can use pgrep to get a list of PIDs by process name then pass them to the -p option of top.

For example:

top -p $(pgrep -d',' http)

Note: the -d',' option delimits the PIDs with commas, which is what is expected by the top -p.
Note 2: top will return a failure message if there are no running processes that match the name you specify in pgrep.

To write the results of top to a file, use the -n 1 option (only one iteration) and redirect the output to your log file.

top -p $(pgrep -d',' http) -n 1 >> your_log_file

To do that every second, perhaps a while loop with a sleep would do?

while :; do top -p $(pgrep -d',' http) -n 1 >> your_log_file; sleep 1; done

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To timestamp each entry, you can append the output of date. E.g.

while :; do top -p $(pgrep -d',' http) -n 1 >> log.txt; date >> log.txt; sleep 1; done