How can I mimic Bash wildcard directory changes using Dockerfile's WORKDIR?

Docker’s Dockerfile instructions do not perform shell wildcard or glob expansion. When you specify:

DOCKERFILECopied
WORKDIR /some/*ing

Docker interprets the literal string “/some/*ing” as the directory path. In other words, WORKDIR does not expand * to match an existing directory (as Bash would). Instead, it creates (if needed) and sets the working directory to “/some/*ing”.

Workarounds

There isn’t a direct equivalent in Dockerfile syntax for glob expansion. However, you can work around this limitation by using a RUN command that executes a shell which will perform wildcard expansion. For example, you can set an environment variable to the resolved directory and then use that variable with WORKDIR:

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FROM some-base-image

# Ensure your parent directory exists
RUN mkdir -p /some

# Use RUN to resolve the wildcard directory name and store it in a file.
# For demonstration, suppose the directory matching /some/*ing exists.
# You might create it first (or it may exist in your base image).
RUN mkdir -p /some/thing

# Resolve the wildcard using shell expansion and save it to an environment variable.
RUN resolved_dir=$(echo /some/*ing) && echo "RESOLVED_DIR=$resolved_dir" >> /envfile

# Source the file and set ENV value (note: this is a workaround and may not work in all contexts)
ENV RESOLVED_DIR=/some/thing

# Then use the environment variable in WORKDIR
WORKDIR ${RESOLVED_DIR}

# Subsequent commands now run with /some/thing as the working directory.
RUN pwd

Important Considerations

• Static vs. Dynamic: Dockerfile instructions like WORKDIR are static. They do not execute through a shell, so they cannot natively evaluate wildcards or shell-specific syntax.
• Build-time vs. Runtime: Any dynamic resolution you attempt (for example, via RUN commands) happens at build time. The result must be explicitly stored (say as an environment variable) so that subsequent instructions can use it.
• Best Practice: It is generally advisable to design your Dockerfile so that the working directory is explicitly known to avoid ambiguity, particularly when switching directories.

In summary, to change to a directory matching a wildcard, you must resolve the directory dynamically with shell commands using RUN, then set an environment variable to use with WORKDIR. There is no direct wildcard support in WORKDIR itself.