Useless cat SH-2002
Consider using cmd < file | .. or cmd file | .. instead. cat is a tool for con"cat"enating files. Reading a single file as input to a program is considered a Useless Use Of Cat (UUOC).
Consider using pgrep instead of grepping ps output SH-2009
If you are just after a pid from a running program, then pgrep is a much safer alternative. Especially if you are also looking for a pid belonging to a certain user or group. pgrep rolls a number of functionalities into one and can eliminate multiple greps, cuts, seds and awks.
Consider grouping multiple command redirects SH-2129
Rather than adding >> something after every single line, you can simply group the relevant commands and redirect the group. Now the file has to be opened and closed only once, which can be a performance gain.
Consider using grep -q SH-2143
grep -q is a more performant way to indicate the existence of one or more matches for a pattern.
Consider using ${variable//search/replace} SH-2001
Consider using parameter expansion to search and replace data. In the problematic code the value is passed to sed to do this, but for simple substitutions, parameter expansion can do it with less overhead.