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##  Code Snippets CLI - Command line code samples
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perl -e "print \"@INC\""

# display date as YYYmmdd  and remove trailing new line - good for filenaming
date +%Y%m%d | tr -d '\n|\r'
or
datestring=$(date +"%Y%m%d")

echo "27 june 2011" | awk '{print "date -d\""$1FS$2FS$3"\" +%Y%m%d"}' | bash
echo "Nov 9, 2020" | awk '{print "date -d\""$1FS$2FS$3"\" +%Y%m%d"}' | bash


# command line script to diff files
# prints the file name in /dir
# diffs it with the same file in pwd
# the -f9 in the cut command means take the 9th delimited field
for i in /dir/* ;
    do   echo $i
    j=`echo $i|cut -d'/' -f9`;
    diff -b $i $j; 
done


# editing batch filename on command line
for i in `ls`; do echo $i; j=`echo $i | (sed s/pre/post/)`; cp $i $j; done


# syntax example of bash "for loop" on command line
for i in $(cat centos_packages.txt) ; do echo $i ; done