file1.txt:
01|bla
02|ble
03|blo
04|blu abb
05|bli

file2.txt:
bla|clanok prvy pwav
blo|clanok druhy avaer
ble|clanok treti
bli|clanok stvrty aofa we
blu abb|clanok piatyyy

VYSTUP: join --header -t '|' -1 2 -2 1 file1.txt file2.txt
MENO_CLANKU|CISLO_CLANKU|TEXT
bla|01|clanok prvy pwav
join: file2.txt:4: is not sorted: ble|clanok treti
blo|03|clanok druhy avaer
join: file1.txt:6: is not sorted: 05|bli
blu abb|04|clanok piatyyy