Some software development tools (correctly) assume that the #include <…> syntax is used for system/language headers and the #include "…" syntax is used for the developer's own headers. So, if the wrong include syntax is used, they fail to properly handle the code. For example, this is a problem with static code analyzers that ignore warnings when the angle brackets are used and that display them when the double quotes are used. This trivial script helps to catch the incorrect include syntaxes.
You can use this script with find . -type | xargs -n 1000 the_script
The old version of this script is available here.

#!/bin/bash



# list of directories containing header files
headerdir="/usr/include \
    /usr/X11R6/include \
    /usr/lib/gcc-lib/i386-redhat-linux/3.2.2/include \
    /usr/lib/gcc-lib/i386-redhat-linux7/2.96/include"




# list of directories in the include path (the subdirectories must be after their directories)
includepath="/usr/include \
    /usr/include/g++-3 \
    /usr/X11R6/include \
    /usr/lib/gcc-lib/i386-redhat-linux/3.2.2/include \
    /usr/lib/gcc-lib/i386-redhat-linux7/2.96/include"



# build list of header files
touch /tmp/the_header_list
for f in $headerdir
    do
        find $f -type f >> /tmp/the_header_list
    done

rincludepath=()
for f in $includepath
    do
        rincludepath="$f $rincludepath"
    done

for f in $rincludepath
    do
        sed "s|$f/||" /tmp/the_header_list > /tmp/the_header_list_
        rm /tmp/the_header_list
        mv /tmp/the_header_list_ /tmp/the_header_list
    done



# loop on the files
for file in $*
do

    stdinc=`grep '#.*include.*<.*>' $file | sed 's/[^<]*<//' | sed 's/>[^>]*//'`
    nstinc=`grep '#.*include.*".*"' $file | sed 's/[^"]*"//' | sed 's/"[^"]*//'`

    for f in $stdinc
    do
        if ! ( grep -x $f /tmp/the_header_list > /dev/null ); then
            echo "cannot find standard $f ($file)"
        fi
    done

    for f in $nstinc
    do
        if ( grep -x $f /tmp/the_header_list > /dev/null ); then
            echo "cannot find non-standard $f ($file)"
        fi
    done

    shift

done

rm /tmp/the_header_list