This shell script takes the file or folder name as its first argument and the label index (0 for no label, 1 for red, ..., 7 for gray) as its second argument.
#!/bin/sh
osascript -e "tell application "Finder" to set label index of alias POSIX file "`cd -P -- "$(dirname -- "$1")" && printf '%s
' "$(pwd -P)/$(basename -- "$1")"`" to $2"
More directly, if $filename is a shell variable with the absolute path name of the file or folder to be labeled and $label is a shell variable with the label index number,
osascript -e "tell application "Finder" to set label index of alias POSIX file "$filename" to $label"
is a shell command to assign the label to the file or folder.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…