ISO-Format JJJJMMTT Alias/Script Linux-CodePudding

Hay everyone,

i want to Implement a dat2iso command as a script or as an alias, which accepts a date in German format DD.MM.YYYY as a parameter and outputs the date in ISO format YYYYMMDD as output (on stdout). Examples (as an alias or as a script in the system path;

outputs: 
$ dat2iso 30.09.2021
20210930
$ dat2iso 01.01.2022
20220101
$ dat2iso 03/10/2021
Error!   <-- Because the separator was. required.
$ dat2iso 03.10.21
Error!   <-- Because the year YYYY was prescribed with four digits.
$ dat2iso 32.09.2021
Error!   <-- Denn einen 32. gibt es nicht.
$ dat2iso 30.13.2021
Error!   <-- Because there is no 13th month.

i have come sofar to change the formate but i cant figure the rest but im still working on it:

echo 30.09.2021 | awk -F '.' {'printf "%s%s%s\n",$3,$2,$1'}

CodePudding user response：

This should achieve what you expected :

#!/bin/bash

dat2iso(){
    if  [[ $1 =~ ^([[:digit:]]{2})\.([[:digit:]]{2})\.([[:digit:]]{4})$ ]]; then
        local date="${BASH_REMATCH[3]}${BASH_REMATCH[2]}${BASH_REMATCH[1]}"
        if  date -d "$date" >& /dev/null; then
            echo "$date"
        else
            echo "Invalid date value [$date]" >&2
        fi
    else
        echo "Invalid format of input [$1]. Correct format [DD.MM.YYYY]" >&2
    fi
}

dat2iso 30.09.2021

CodePudding user response：

A very verbose solution, but it checks for your given exemptions:

cat << EOF > dat2iso
#!/bin/bash

if [[ "\$1" == "" ]];then echo -e "NO INPUT. Exiting."; exit 1 ;fi

echo \$1 | awk -F '.' '/\//{ print "Input Error."; exit(1) }
   \$1>31{ print "Too many days."; exit(1) }
   \$2>12{ print "Too many months."; exit(1) }
   \$3!~/[[:digit:]][[:digit:]][[:digit:]][[:digit:]]/{ print "Not enough year digits."; exit(1) }
   { print \$3\$2\$1 }'
EOF

chmod  x dat2iso

$ ./dat2iso 09.12.2021
20211209