Bash PWD缩短

Question

我正在寻找一个bash函数，它可以缩短长路径名，以防止我的PS1变量变得过长。大致是这样的：

/this/is/the/path/to/a/really/long/directory/i/would/like/shortened

可能会以如下方式结束：

/t../i../t../p../to/a/r../l../d../i/w../like/shortened

采用路径和最大可接受字符数来缩短的内容对于我的.bashrc文件来说将是完美的。

Answer 1

Python脚本怎么样？这将首先缩短最长的目录名，一次缩短一个字符，直到它达到其长度目标，或者无法使路径更短。它不会缩短路径中的最后一个目录。

(我一开始是用普通的shell脚本编写这段代码，但是bash在字符串操作方面很糟糕。)

#!/usr/bin/env python
import sys

try:
    path   = sys.argv[1]
    length = int(sys.argv[2])
except:
    print >>sys.stderr, "Usage: $0 <path> <length>"
    sys.exit(1)

while len(path) > length:
    dirs = path.split("/");

    # Find the longest directory in the path.
    max_index  = -1
    max_length = 3

    for i in range(len(dirs) - 1):
        if len(dirs[i]) > max_length:
            max_index  = i
            max_length = len(dirs[i])

    # Shorten it by one character.    
    if max_index >= 0:
        dirs[max_index] = dirs[max_index][:max_length-3] + ".."
        path = "/".join(dirs)

    # Didn't find anything to shorten. This is as good as it gets.
    else:
        break

print path

输出示例：

$ echo $DIR
/this/is/the/path/to/a/really/long/directory/i/would/like/shortened
$ ./shorten.py $DIR 70
/this/is/the/path/to/a/really/long/directory/i/would/like/shortened 
$ ./shorten.py $DIR 65
/this/is/the/path/to/a/really/long/direc../i/would/like/shortened
$ ./shorten.py $DIR 60
/this/is/the/path/to/a/re../long/di../i/would/like/shortened
$ ./shorten.py $DIR 55
/t../is/the/p../to/a/r../l../di../i/wo../like/shortened
$ ./shorten.py $DIR 50
/t../is/the/p../to/a/r../l../d../i/w../l../shortened

Answer 2

没有给出相同的结果，但是我的~/.bashrc包含

_PS1 ()
{
    local PRE= NAME="$1" LENGTH="$2";
    [[ "$NAME" != "${NAME#$HOME/}" || -z "${NAME#$HOME}" ]] &&
        PRE+='~' NAME="${NAME#$HOME}" LENGTH=$[LENGTH-1];
    ((${#NAME}>$LENGTH)) && NAME="/...${NAME:$[${#NAME}-LENGTH+4]}";
    echo "$PRE$NAME"
}
PS1='\u@\h:$(_PS1 "$PWD" 20)\$ '

这将显示的路径限制为最多20个字符。如果路径超过20个字符，它将显示为/...d/like/shortened或~/.../like/shortened。

Answer 3

这里有一个您可能会喜欢的bash解决方案。这会将路径的每个部分缩短到仍然可以用制表符完成的最短前缀，并使用*代替..。作为填充物。

#!/bin/bash

begin="" # The unshortened beginning of the path.
shortbegin="" # The shortened beginning of the path.
current="" # The section of the path we're currently working on.
end="${2:-$(pwd)}/" # The unmodified rest of the path.
end="${end#/}" # Strip the first /
shortenedpath="$end" # The whole path, to check the length.
maxlength="${1:-0}"

shopt -q nullglob && NGV="-s" || NGV="-u" # Store the value for later.
shopt -s nullglob    # Without this, anything that doesn't exist in the filesystem turns into */*/*/...

while [[ "$end" ]] && (( ${#shortenedpath} > maxlength ))
do
  current="${end%%/*}" # everything before the first /
  end="${end#*/}"    # everything after the first /

  shortcur="$current"
  shortcurstar="$current" # No star if we don't shorten it.

  for ((i=${#current}-2; i>=0; i--))
  do
    subcurrent="${current:0:i}"
    matching=("$begin/$subcurrent"*) # Array of all files that start with $subcurrent. 
    (( ${#matching[*]} != 1 )) && break # Stop shortening if more than one file matches.
    shortcur="$subcurrent"
    shortcurstar="$subcurrent*"
  done

  begin="$begin/$current"
  shortbegin="$shortbegin/$shortcurstar"
  shortenedpath="$shortbegin/$end"
done

shortenedpath="${shortenedpath%/}" # strip trailing /
shortenedpath="${shortenedpath#/}" # strip leading /

echo "/$shortenedpath" # Make sure it starts with /

shopt "$NGV" nullglob # Reset nullglob in case this is being used as a function.

将长度作为第一个参数，将路径作为可选的第二个参数。如果没有给出第二个参数，它将使用当前工作目录。

这将尝试缩短到给定的长度以下。如果这是不可能的，它只给出它能给出的最短路径。

从算法上讲，这可能很可怕，但它最终是相当快的。(快速shell脚本的关键是避免子shell和外部命令，尤其是在内部循环中。)

根据设计，它只能缩短2个或更多字符('hom*‘与’home‘的字符数相同)。

这并不完美。在某些情况下，它不会尽可能地缩短，比如如果有几个文件的文件名共享一个前缀(如果存在foobar1和foobar2，则不会缩短foobar3 )。