OS X terminal command to resolve path of an alias

Question

I'm writing a shell script which will rsync files from remote machines, some linux, some macs, to a central backup server. The macs have folders on the root level containing aliases of all files/folders which need to be backed up. What is a terminal command I can use to resolve the path to the files/folders the aliases point to? (I'll need to pass these paths to rsync)

Answer 1

I had this problem and so I've implemented a command-line tool. It's open source at https://github.com/rptb1/aliasPath

The key thing is that it will work even if the alias is broken, unlike any AppleScript solution I've found. You can therefore use it to write scripts to fix aliases when lots of files change volume. That's why I wrote it.

The source code is very short, but here's a summary of the key part, for anyone else needing to solve this problem in code, or who wants to look up the relevant protocols.

NSString *aliasPath = [NSString stringWithUTF8String:posixPathToAlias];
NSURL *aliasURL = [NSURL fileURLWithPath:aliasPath];
NSError *error;
NSData *bookmarkData = [NSURL bookmarkDataWithContentsOfURL:aliasURL error:&error];
NSDictionary *values = [NSURL resourceValuesForKeys:@[NSURLPathKey]
                                   fromBookmarkData:bookmarkData];
NSString *path = [values objectForKey:NSURLPathKey];
const char *s = [path UTF8String];

Answer 2

I found the following script which does what I needed:

#!/bin/sh
if [ $# -eq 0 ]; then
  echo ""
  echo "Usage: $0 alias"
  echo "  where alias is an alias file."
  echo "  Returns the file path to the original file referenced by a"
  echo "  Mac OS X GUI alias.  Use it to execute commands on the"
  echo "  referenced file.  For example, if aliasd is an alias of"
  echo "  a directory, entering"
  echo '   % cd `apath aliasd`'
  echo "  at the command line prompt would change the working directory"
  echo "  to the original directory."
  echo ""
fi
if [ -f "$1" -a ! -L "$1" ]; then
    # Redirect stderr to dev null to suppress OSA environment errors
    exec 6>&2 # Link file descriptor 6 with stderr so we can restore stderr later
    exec 2>/dev/null # stderr replaced by /dev/null
    path=$(osascript << EOF
tell application "Finder"
set theItem to (POSIX file "${1}") as alias
if the kind of theItem is "alias" then
get the posix path of ((original item of theItem) as text)
end if
end tell
EOF
)
    exec 2>&6 6>&-      # Restore stderr and close file descriptor #6.

    echo "$path"
fi

Answer 3

I've found this tool.

A tiny bit of compiled code, a function in your .bash_profile, and voila. Transparent handling of aliases, just use "cd". Several times faster than using Applescript, too.