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Paul Jurczak
Asked: 2024-01-29 14:44:54 +0800 CST

Why apt is not finding already installed package? [duplicate]

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On Ubuntu 22.04.3:

paul@box4x4:~$ apt search libstdc++ | grep installed

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

libstdc++-11-dev/jammy-updates,jammy-security,now 11.4.0-1ubuntu1~22.04 amd64 [installed,automatic]
libstdc++-12-dev/jammy-updates,jammy-security,now 12.3.0-1ubuntu1~22.04 amd64 [installed]
libstdc++6/jammy-updates,jammy-security,now 12.3.0-1ubuntu1~22.04 amd64 [installed,automatic]

which shows that libstdc++-12-dev is already installed. Searching for it with:

paul@box4x4:~$ apt search libstdc++-12-dev
Sorting... Done
Full Text Search... Done

fails. Why is that?

apt

1 Answers

  1. Best Answer

    Run apt search libstdc\\+\\+-12-dev instead.

    man apt says:

      search (apt-cache(8))
      search can be used to search for the given regex(7) term(s)

    No, this is not a problem with bash expansion. If it was doing expansion, echo will help you debug what it is expanding to:

    home@daniel-tablet1:~$ echo apt search libstdc++-12-dev
apt search libstdc++-12-dev
home@daniel-tablet1:~$ echo apt search 'libstdc++-12-dev'
apt search libstdc++-12-dev

    The problem is that you wrote libstdc++-12-dev. This, when interpreted as a RegEx, means:

    • The string libstd literally
    • In effect, any number of c's. Literally, or more matches of the preceding, namely:
      • In effect, any number of c's. Literally, or more matches of the preceding, namely: (Having this nested twice is redundant)
        • The string c literally
    • The string -12-dev literally

    apt search 'libstdc\+\+-12-dev' works just as well as apt search libstdc\\+\\+-12-dev. To escape the backslashes from bash, you either need to quote or double them. Then, the apt RegEx engine needs a backslash to tell it to interpret + as a literal string instead of "one or more of the preceding."

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