给定一个绝对路径或相对路径(在类unix系统中),我希望在解析任何中间符号链接之后确定目标的完整路径。同时还可以解析~用户名符号。

如果目标是一个目录,则可以将chdir()放入该目录,然后调用getcwd(),但我确实希望从shell脚本而不是编写C helper来完成此操作。不幸的是,shell倾向于试图向用户隐藏符号链接的存在(这是OS X上的bash):

$ ls -ld foo bar
drwxr-xr-x   2 greg  greg  68 Aug 11 22:36 bar
lrwxr-xr-x   1 greg  greg   3 Aug 11 22:36 foo -> bar
$ cd foo
$ pwd
/Users/greg/tmp/foo
$

我想要的是一个函数resolve(),这样当从上面的例子中的tmp目录执行时,resolve("foo") == "/Users/greg/tmp/bar"。


当前回答

试试这个:

cd $(dirname $([ -L $0 ] && readlink -f $0 || echo $0))

其他回答

另一种方法:

# Gets the real path of a link, following all links
myreadlink() { [ ! -h "$1" ] && echo "$1" || (local link="$(expr "$(command ls -ld -- "$1")" : '.*-> \(.*\)$')"; cd $(dirname $1); myreadlink "$link" | sed "s|^\([^/].*\)\$|$(dirname $1)/\1|"); }

# Returns the absolute path to a command, maybe in $PATH (which) or not. If not found, returns the same
whereis() { echo $1 | sed "s|^\([^/].*/.*\)|$(pwd)/\1|;s|^\([^/]*\)$|$(which -- $1)|;s|^$|$1|"; } 

# Returns the realpath of a called command.
whereis_realpath() { local SCRIPT_PATH=$(whereis $1); myreadlink ${SCRIPT_PATH} | sed "s|^\([^/].*\)\$|$(dirname ${SCRIPT_PATH})/\1|"; } 

因为我在过去的几年里遇到过很多次这样的情况,这一次我需要一个纯粹的bash可移植版本,可以在OSX和linux上使用,我继续写了一个:

活生生的版本就在这里:

https://github.com/keen99/shell-functions/tree/master/resolve_path

但为了SO,这里是当前的版本(我觉得它经过了很好的测试..但我愿意接受反馈!)

可能不难使它为普通bourne shell (sh)工作,但我没有尝试…我太喜欢$FUNCNAME了。:)

#!/bin/bash

resolve_path() {
    #I'm bash only, please!
    # usage:  resolve_path <a file or directory> 
    # follows symlinks and relative paths, returns a full real path
    #
    local owd="$PWD"
    #echo "$FUNCNAME for $1" >&2
    local opath="$1"
    local npath=""
    local obase=$(basename "$opath")
    local odir=$(dirname "$opath")
    if [[ -L "$opath" ]]
    then
    #it's a link.
    #file or directory, we want to cd into it's dir
        cd $odir
    #then extract where the link points.
        npath=$(readlink "$obase")
        #have to -L BEFORE we -f, because -f includes -L :(
        if [[ -L $npath ]]
         then
        #the link points to another symlink, so go follow that.
            resolve_path "$npath"
            #and finish out early, we're done.
            return $?
            #done
        elif [[ -f $npath ]]
        #the link points to a file.
         then
            #get the dir for the new file
            nbase=$(basename $npath)
            npath=$(dirname $npath)
            cd "$npath"
            ndir=$(pwd -P)
            retval=0
            #done
        elif [[ -d $npath ]]
         then
        #the link points to a directory.
            cd "$npath"
            ndir=$(pwd -P)
            retval=0
            #done
        else
            echo "$FUNCNAME: ERROR: unknown condition inside link!!" >&2
            echo "opath [[ $opath ]]" >&2
            echo "npath [[ $npath ]]" >&2
            return 1
        fi
    else
        if ! [[ -e "$opath" ]]
         then
            echo "$FUNCNAME: $opath: No such file or directory" >&2
            return 1
            #and break early
        elif [[ -d "$opath" ]]
         then 
            cd "$opath"
            ndir=$(pwd -P)
            retval=0
            #done
        elif [[ -f "$opath" ]]
         then
            cd $odir
            ndir=$(pwd -P)
            nbase=$(basename "$opath")
            retval=0
            #done
        else
            echo "$FUNCNAME: ERROR: unknown condition outside link!!" >&2
            echo "opath [[ $opath ]]" >&2
            return 1
        fi
    fi
    #now assemble our output
    echo -n "$ndir"
    if [[ "x${nbase:=}" != "x" ]]
     then
        echo "/$nbase"
    else 
        echo
    fi
    #now return to where we were
    cd "$owd"
    return $retval
}

这里有一个经典的例子,感谢brew:

%% ls -l `which mvn`
lrwxr-xr-x  1 draistrick  502  29 Dec 17 10:50 /usr/local/bin/mvn@ -> ../Cellar/maven/3.2.3/bin/mvn

使用这个函数,它将返回-real- path:

%% cat test.sh
#!/bin/bash
. resolve_path.inc
echo
echo "relative symlinked path:"
which mvn
echo
echo "and the real path:"
resolve_path `which mvn`


%% test.sh

relative symlinked path:
/usr/local/bin/mvn

and the real path:
/usr/local/Cellar/maven/3.2.3/libexec/bin/mvn 

在这里,我提出了一个我认为是跨平台(至少Linux和macOS)的解决方案,目前对我来说效果很好。

crosspath()
{
    local ref="$1"
    if [ -x "$(which realpath)" ]; then
        path="$(realpath "$ref")"
    else
        path="$(readlink -f "$ref" 2> /dev/null)"
        if [ $? -gt 0 ]; then
            if [ -x "$(which readlink)" ]; then
                if [ ! -z "$(readlink "$ref")" ]; then
                    ref="$(readlink "$ref")"
                fi
            else
                echo "realpath and readlink not available. The following may not be the final path." 1>&2
            fi
            if [ -d "$ref" ]; then
                path="$(cd "$ref"; pwd -P)"
            else
                path="$(cd $(dirname "$ref"); pwd -P)/$(basename "$ref")"
            fi
        fi
    fi
    echo "$path"
}

这里有一个macOS(仅?)解决方案。也许更适合最初的问题。

mac_realpath()
{
    local ref="$1"
    if [[ ! -z "$(readlink "$ref")" ]]; then
        ref="$(readlink "$1")"
    fi
    if [[ -d "$ref" ]]; then
        echo "$(cd "$ref"; pwd -P)"
    else
        echo "$(cd $(dirname "$ref"); pwd -P)/$(basename "$ref")"
    fi
}

下面是如何使用内联Perl脚本在MacOS/Unix中获得文件的实际路径:

FILE=$(perl -e "use Cwd qw(abs_path); print abs_path('$0')")

类似地,要获取符号链接文件的目录:

DIR=$(perl -e "use Cwd qw(abs_path); use File::Basename; print dirname(abs_path('$0'))")
function realpath {
    local r=$1; local t=$(readlink $r)
    while [ $t ]; do
        r=$(cd $(dirname $r) && cd $(dirname $t) && pwd -P)/$(basename $t)
        t=$(readlink $r)
    done
    echo $r
}

#example usage
SCRIPT_PARENT_DIR=$(dirname $(realpath "$0"))/..