从sql文件中提取drop

#!/usr/bin/env bash
set -e
# 
# filename prefix
#     fs_|ft_ : function return string or table
#     p_      : procedure
#     t_      : table
#     dt_     : table data
#     check_  : check create sql data with selct
#     task_   : timing task
#
# point
#     1. drop sql before create sql, so head -n 20 is ok.
#     2. function/table/procedure must drop before create,
# so show WARNGIN when not found drop sql
#     3. only fs_|ft_|p_|t_ prefix file need be checked.
#
# shell
#     1. wc -l : count rows
#     2. grep
#            -E : regexp
#            -A : show more rows after founded row
#            -B : show more row before founded row
#            -m : only show the first found result
#            \b : word boundary, \bok\b, ok => yes, itsok => no
#     3. basename/dirname
#     4. &&     : if true then continue
#        ||     : if false then continue
#        eg: test 1 -eq 1 && echo '==' || echo '!='
#     5. \      : one line shell break row
#
# main function: 
extract ()
{
    sqlpath=$1;
    sqlfile=$2;
    keyword=$3;

    num=$(ls ${sqlpath}/*.sql | grep -E "${keyword}" | wc -l)
    echo "----- ${keyword} \n----- [${num}] \n\n" >> ${sqlfile}

    ls ${sqlpath}/*.sql | grep -E "${keyword}" | \
    while read file;
    do 
        filename=$(basename "${file}")
        dropsql=$(cat "${file}" | head -n 20 | grep -A 1 -B 1 -m 1 "\bdrop\b" || echo "notfound")

        if [ "${dropsql}" = "notfound" ]; then
            echo "WARNGING: not found drop sql in first 20 rows - ${filename}"
        else
            echo "-- ${filename}\n${dropsql}" >> ${sqlfile}
        fi;
    done
    #cat ${sqlpath}/*.sql | grep -A 1 -B 1 -m 1 "${keyword}" >> ${sqlfile}
}

sqlpath=$(pwd)/sql
sqlfile=$(pwd)/drop.sql

# clear sql file
true > ${sqlfile}

# extract table
extract ${sqlpath} ${sqlfile} "\<t_"

# extract function
extract ${sqlpath} ${sqlfile} "\<fs_|\<ft_"

# extract procedure
extract ${sqlpath} ${sqlfile} "\<p_"