Invoke and track memory usage of one process

This should do what you need. It gets the information from /proc/$PID/statm and prints (from man procfs):

              size       total program size
                         (same as VmSize in /proc/[pid]/status)
              resident   resident set size
                         (same as VmRSS in /proc/[pid]/status)
              share      shared pages (from shared mappings)
              data       data + stack

The script:

#!/usr/bin/env bash 

## Print header
 echo -e "Size\tResid.\tShared\tData\t%"
 while [ 1 ]; do
    ## Get the PID of the process name given as argument 1
     pidno=`pgrep $1`
    ## If the process is running, print the memory usage
     if [ -e /proc/$pidno/statm ]; then
     ## Get the memory info
      m=`awk '{OFS="\t";print $1,$2,$3,$6}' /proc/$pidno/statm`
     ## Get the memory percentage
      perc=`top -bd .10 -p $pidno -n 1  | grep $pidno | gawk '{print \$10}'`
     ## print the results
      echo -e "$m\t$perc";
    ## If the process is not running
     else
      echo "$1 is not running";
     fi
 done

You can then call the script, giving it a process name as input. For example:

$ memusage.sh firefox
Size    Resid.  Shared  Data    %
517193  261902  9546    400715  12.8
517193  261902  9546    400715  12.8
517193  261902  9546    400715  12.8
517193  262100  9546    400715  12.8
517193  262100  9546    400715  12.8
517193  262100  9546    400715  12.8
517209  261899  9546    400731  12.8
517209  261899  9546    400731  12.8

NOTES:

• This assumes that there is only a single running process with the name specified.