Results for “command substitution”
Small, practical examples. Search by task or narrow things down below.
Pass dollar expressions through Compose
Docker / Compose: Double dollar signs defer expansion to the container shell.
Docker / Compose✓ Tested
Pass named parameters from a hashtable
Keep a command’s options together in a reusable object.
splatting✓ Tested
Pipe input into a container process
Docker / Compose: The interactive flag keeps standard input open without allocating a terminal.
Docker / Compose✓ Tested
Prepare an owned directory before dropping root
Docker / Compose: Create and chown the writable application path before USER.
Docker / Compose✓ Tested
Preserve a failure status while an EXIT trap runs
Bash Scripts: Capture the status immediately on entry to the trap before running cleanup commands.
Bash Scripts✓ Tested
Prevent gaining privileges through exec
Docker / Compose: The no-new-privileges flag is visible in process status.
Docker / Compose✓ Tested
Protect a Compose service’s root filesystem
Docker / Compose: read_only rejects writes to the image filesystem.
Docker / Compose✓ Tested
Provide a default environment value
Set a runtime default that can be overridden at startup.
Dockerfile✓ Tested
Put an optional service behind a profile
Keep a utility service separate from a normal Compose startup.
Compose✓ Tested
Read a completed example’s output
Docker / Compose: Read a completed example’s output using a locally available Ubuntu image.
Docker / Compose✓ Tested
Read a field from container metadata
Use an inspect template for stable machine-readable output.
inspect✓ Tested
Read a secret from a mounted file
Docker / Compose: Compose secrets make a file available under /run/secrets.
Docker / Compose✓ Tested