SC2058 – ShellCheck Wiki

Unknown unary operator.

Problematic code:

[ -E 42 ]

Correct code:

[ -e 42 ]

Rationale:

You are using an unknown unary operator in a test expression. Perhaps it's a typo?

In bash, you can use help test to see a list of supported operators:

  -a FILE        True if file exists.
  -b FILE        True if file is block special.
  -c FILE        True if file is character special.
  -d FILE        True if file is a directory.
  -e FILE        True if file exists.
  -f FILE        True if file exists and is a regular file.
  -g FILE        True if file is set-group-id.
  -h FILE        True if file is a symbolic link.
  -L FILE        True if file is a symbolic link.
  -k FILE        True if file has its `sticky' bit set.
  -p FILE        True if file is a named pipe.
  -r FILE        True if file is readable by you.
  -s FILE        True if file exists and is not empty.
  -S FILE        True if file is a socket.
  -t FD          True if FD is opened on a terminal.
  -u FILE        True if the file is set-user-id.
  -w FILE        True if the file is writable by you.
  -x FILE        True if the file is executable by you.
  -O FILE        True if the file is effectively owned by you.
  -G FILE        True if the file is effectively owned by your group.
  -N FILE        True if the file has been modified since it was last read.

Exceptions:

None. If you've tested and verified that the operator works but the latest version of ShellCheck says it's unknown, please submit a bug report.

The classic test command on the Bash Hackers wiki.
The conditional expression on the Bash Hackers wiki.
Tests and conditionals on the Wooledge BashGuide.