Hi, keep in mind that the quotation marks, wildcard characters, and variables are interpreted by the shell parser, not by the program you run. By quoting you control what the program will get to see as its list of arguments.
Hans wrote: > 1. apt-get --purge remove 4.3.1-0-* Without quotation marks around "*", the shell parser will list all file names which match the search pattern "4.3.1-0-*". Assumed that the current directory contains these files 1234-5678.foo 4.3.1-0-foo 4.3.1-0-bar another_file one_more the program apt-get will get to see these four arguments: --purge remove 4.3.1-0-foo 4.3.1-0-bar > 2. aptitude purge '~n4.3.1-0-*' With the hard quotation marks arount it, the shell parser will just unpack the text and use it as a single argument. aptitude will see two arguments: purge ~n4.3.1-0-* I assume aptitude shall use the second argument for an own search operation, which differs from what the shell parser would do. > 3. aptitude purge 'deborphan --guess-all' Again the shell parser will just unpack the content of the quotes. This time they shall not prevent interpretation of "*" but the splitting into two words at the blank character. aptitude will see two arguments purge deborphan --guess-all Here i assume, that aptitude shall learn a command line which it will execute on its own discretion. https://www.debian-administration.org/article/134/Removing_unnecessary_packages_with_deborphan Since no variable evaluations are in the string, one could as well have wrapped it in "-quotes. > At the moment I find no example for "foo", Let's invent some: x=foo y=bar echo "$x - $y" lets echo see and print the single argument foo - bar That's because "-quotes do not prevent evaluation of shell variables by the shell parser. > I see no system behind it. Looks weired for me. There are the general rules for the shell parser and the particular expectations of the programs towards their arguments. Quotation marks are needed as soon as the program shall be fed with arguments which the shell parser would convert in an undesired way. ------------------------------------------------------------------ If you want to see the effect of a list of arguments, try this contraption for i in --purge remove 4.3.1-0-* ; do echo "$i" ; done should in above example situation print --purge remove 4.3.1-0-foo 4.3.1-0-bar whereas for i in '4.3.1-0-*' ; do echo "$i" ; done will always print 4.3.1-0-* Have a nice day :) Thomas
