Shell Programming and Scripting

$ false | true
$ echo $?
0
$ set -o pipefail
$ false | true
$ echo $?
1

$ true | false | true | false
$ echo ${PIPESTATUS[*]}
0 1 0 1

$ true | false | true | false
$ foo=( ${PIPESTATUS[*]} )
$ echo ${keepme[*]}
0 1 0 1

 with any other Bourne like shells

       You need to use a trick to pass the exit codes to the main
       shell.  You can do it using a pipe(2). Instead of running
       "cmd1", you run "cmd1; echo $?" and make sure $? makes it way
       to the shell.

       exec 3>&1
       eval `
         # now, inside the `...`, fd4 goes to the pipe
         # whose other end is read and passed to eval;
         # fd1 is the normal standard output preserved
         # the line before with exec 3>&1
         exec 4>&1 >&3 3>&-
         {
           cmd1 4>&-; echo "ec1=$?;" >&4
         } | {
           cmd2 4>&-; echo "ec2=$?;" >&4
         } | cmd3
         echo "ec3=$?;" >&4
       `