How to escape single quotes correctly creating an alias

Question

I've been given this one-liner to know how much memory my processes consume.

$ ps -u $USER -o pid,rss,command | \
    awk '{print $0}{sum+=$2} END {print "Total", sum/1024, "MB"}'

Now I'd like to create an alias for that command, but have an issue escaping ' characters:

$ alias mm=ps -u $USER -o pid,rss,command | \
    awk '{print $0}{sum+=$2} END {print "Total", sum/1024, "MB"}'
bash: alias: -u: not found
bash: alias: myuser: not found
bash: alias: -o: not found
bash: alias: pid,rss,command: not found
Total 0 MB

I tried to escape the single quotes, but still it doesn't work.

$ alias mm='ps -u $USER -o pid,rss,command | \
    awk \'{print $0}{sum+=$2} END {print "Total", sum/1024, "MB"}\''
> 

Can you help me understand how to create this alias?

Solution 1

To make this an alias, which is possible, you need to use double quotes around the entire value for the alias. You'll also need to escape a few things within the alias as a result, and you need to escape any of the field arguments to awk since these will get interpreted as arguments by Bash as well when you're setting the alias.

This worked for me:

$ alias mm="ps -u $USER -o pid,rss,command | \
    awk '{print \$0}{sum+=\$2} END {print \"Total\", sum/1024, \"MB\"}'"

In the above I've done the following:

1. Double quotes around alias' value

   alias mm="ps -u ...."
   

2. Escaped awk's double quotes

   awk '{print \$0}{sum+=\$2} END {print \"Total\", sum/1024, \"MB\"}
   

3. Escaped awk's fields

   awk '{print \$0}{sum+=\$2} END
   

Would I use this?

Probably not, I'd switch this to a Bash function instead, since it'll be easier to maintain and understand what's going on, but here's the alias if you still want it.

Solution 2

Can you help me understand how to create this alias?

May I advise you to create a function if you use bash and put it in .bashrc?

mm() {
  ps -u "$USER" -o pid,rss,command |
    awk '{print $0}{sum+=$2}
         END {print "Total", sum/1024, "MB"}'
}

If it's bash, variables need to be quoted. In a function, no need to put everything on one line.

Solution 3

Here is escaped command:

alias mm='ps -u $USER -o pid,rss,command | \
    awk '\''{print $0}{sum+=$2} END {print "Total", sum/1024, "MB"}'\'

Example of escaping quotes in shell:

$ echo 'abc'\''abc'
abc'abc
$ echo "abc"\""abc"
abc"abc

It's simply done by finishing already opened one ('), placing escaped one (\'), then opening another one (').

Alternatively:

$ echo 'abc'"'"'abc'
abc'abc
$ echo "abc"'"'"abc"
abc"abc

It's done by finishing already opened one ('), placing quote in another quote ("'"), then opening another one (').

Related: How to escape single-quotes within single-quoted strings? at stackoverflow SE

Comments

[Adrian Pronk]

stackoverflow.com/q/1250079/41861