In Linux, how to tell how much memory processes are using?

Question

I think I may have a memory leak in my LAMP application (memory gets used up, swap starts getting used, etc.). If I could see how much memory the various processes are using

Answer 1

In case you don't have a current or long running process to track, you can use /usr/bin/time.

This is not the same as Bash time (as you will see).

Eg

# /usr/bin/time -f "%M" echo

2028

This is "Maximum resident set size of the process during its lifetime, in Kilobytes" (quoted from the man page). That is, the same as RES in top et al.

There are a lot more you can get from /usr/bin/time.

# /usr/bin/time -v echo

Command being timed: "echo"
User time (seconds): 0.00
System time (seconds): 0.00
Percent of CPU this job got: 0%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.00
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 1988
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 77
Voluntary context switches: 1
Involuntary context switches: 0
Swaps: 0
File system inputs: 0
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0