The shell has other wildcards as well, though they are less commonly used:
? matches a single character, so 201?.txt will match 2017.txt or 2018.txt, but not 2017-01.txt.[...] matches any one of the characters inside the square brackets, so 201[78].txt matches 2017.txt or 2018.txt, but not 2016.txt.{...} matches any of the comma-separated patterns inside the curly brackets, so {*.txt, *.csv} matches any file whose name ends with .txt or .csv, but not files whose names end with .pdf.Which expression would match singh.pdf and johel.txt but not sandhu.pdf or sandhu.txt?