bash中有没有将字符串转换为小写字符串的方法?

例如,如果我有:

a="Hi all"

我想将其转换为:

"hi all"

当前回答

tr:

a="$(tr [A-Z] [a-z] <<< "$a")"

AWK:

{ print tolower($0) }

sed:

y/ABCDEFGHIJKLMNOPQRSTUVWXYZ/abcdefghijklmnopqrstuvwxyz/

其他回答

这不是比一个完整的shell变量链+声明+求值+单引号转义+echo+管道+tr更干净吗?

#***仅对于ASCII更快***mawk‘$!NF=上限($_)'<<<'abcxyz'

ABCXYZ

gawk“$_=tolower($_)”<<<“FAB-EDC”

fab-edc

和Unicode一样容易使用,无需“解包”、“编码”或“解码”字节

printf“%s”“${test_utf8}”|……

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……|gawk“$_=toupper($_)”

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在Bash 4中:

小写

$ string="A FEW WORDS"
$ echo "${string,}"
a FEW WORDS
$ echo "${string,,}"
a few words
$ echo "${string,,[AEIUO]}"
a FeW WoRDS

$ string="A Few Words"
$ declare -l string
$ string=$string; echo "$string"
a few words

大写

$ string="a few words"
$ echo "${string^}"
A few words
$ echo "${string^^}"
A FEW WORDS
$ echo "${string^^[aeiou]}"
A fEw wOrds

$ string="A Few Words"
$ declare -u string
$ string=$string; echo "$string"
A FEW WORDS

切换(未记录,但可在编译时配置)

$ string="A Few Words"
$ echo "${string~~}"
a fEW wORDS
$ string="A FEW WORDS"
$ echo "${string~}"
a FEW WORDS
$ string="a few words"
$ echo "${string~}"
A few words

大写(未记录,但可在编译时配置)

$ string="a few words"
$ declare -c string
$ string=$string
$ echo "$string"
A few words

标题大小写:

$ string="a few words"
$ string=($string)
$ string="${string[@]^}"
$ echo "$string"
A Few Words

$ declare -c string
$ string=(a few words)
$ echo "${string[@]}"
A Few Words

$ string="a FeW WOrdS"
$ string=${string,,}
$ string=${string~}
$ echo "$string"
A few words

要关闭声明属性,请使用+。例如,声明+c字符串。这会影响后续赋值,而不是当前值。

declare选项更改变量的属性,但不更改内容。示例中的重新分配会更新内容以显示更改。

编辑:

按照ghostdog74的建议,添加了“按单词切换第一个字符”(${var~})。

编辑:更正波浪号行为以匹配Bash 4.3。

tr:

a="$(tr [A-Z] [a-z] <<< "$a")"

AWK:

{ print tolower($0) }

sed:

y/ABCDEFGHIJKLMNOPQRSTUVWXYZ/abcdefghijklmnopqrstuvwxyz/

因此,我尝试对每个实用程序使用共识方法执行一些更新的基准测试,但我没有多次重复一个小集合,而是。。。

以UTF-8编码的多字节Unicode字符填充到边缘的1.85 GB.txt文件中,为了均衡I/O方面,同时还强制所有人使用LC_ALL=C,以确保公平竞争

————————————————————————————————————————

准确地说,bsd-sed和gnu-sed都相当平庸。我甚至不知道bsd sed在做什么,因为他们的xxhash不匹配python3是否试图使用Unicode字母大小写?(即使我已经强制设置了区域设置LC_ALL=C)tr是最极端的到目前为止,gnutr是最快的bsd tr非常残暴perl5比我拥有的任何awk变体都快,除非你可以使用mawk2一次加载整个文件,以便稍微超过perl5:2.935秒mawk2对每15秒3.081秒在awk中,gnu-gawk的速度最慢,中间是mawk 1.3.4,最快是mawk1.9.9.6:比gawk节省50%以上的时间.(我没有把时间浪费在无用的macosx nawk上)

.

     out9: 1.85GiB 0:00:03 [ 568MiB/s] [ 568MiB/s] [ <=> ]
      in0: 1.85GiB 0:00:03 [ 568MiB/s] [ 568MiB/s] [============>] 100%            
( pvE 0.1 in0 < "${m3t}" | LC_ALL=C mawk2 '{ print tolower($_) }' FS='^$'; )  

mawk 1.9.9.6 (mawk2-beta)

3.07s user 0.66s system 111% cpu 3.348 total
85759a34df874966d096c6529dbfb9d5  stdin


     out9: 1.85GiB 0:00:06 [ 297MiB/s] [ 297MiB/s] [ <=> ]
      in0: 1.85GiB 0:00:06 [ 297MiB/s] [ 297MiB/s] [============>] 100%            
( pvE 0.1 in0 < "${m3t}" | LC_ALL=C mawk '{ print tolower($_) }' FS='^$'; )  

 mawk 1.3.4

6.01s user 0.83s system 107% cpu 6.368 total
85759a34df874966d096c6529dbfb9d5  stdin

     out9: 23.8MiB 0:00:00 [ 238MiB/s] [ 238MiB/s] [ <=> ]
      in0: 1.85GiB 0:00:07 [ 244MiB/s] [ 244MiB/s] [============>] 100%            
     out9: 1.85GiB 0:00:07 [ 244MiB/s] [ 244MiB/s] [ <=>                             ]
( pvE 0.1 in0 < "${m3t}" | LC_ALL=C gawk -be '{ print tolower($_) }' FS='^$';  

GNU Awk 5.1.1, API: 3.1 (GNU MPFR 4.1.0, GNU MP 6.2.1) 

7.49s user 0.78s system 106% cpu 7.763 total
85759a34df874966d096c6529dbfb9d5  stdin


     out9: 1.85GiB 0:00:03 [ 616MiB/s] [ 616MiB/s] [ <=> ]
      in0: 1.85GiB 0:00:03 [ 617MiB/s] [ 617MiB/s] [============>] 100%            
( pvE 0.1 in0 < "${m3t}" | LC_ALL=C perl -ne 'print lc'; )  

perl5 (revision 5 version 34 subversion 0)

2.70s user 0.85s system 115% cpu 3.081 total
85759a34df874966d096c6529dbfb9d5  stdin


     out9: 1.85GiB 0:00:32 [57.4MiB/s] [57.4MiB/s] [ <=> ]
      in0: 1.85GiB 0:00:32 [57.4MiB/s] [57.4MiB/s] [============>] 100%            
( pvE 0.1 in0 < "${m3t}" | LC_ALL=C gsed 's/.*/\L&/'; )  # GNU-sed


gsed (GNU sed) 4.8

32.57s user 0.97s system 101% cpu 32.982 total
85759a34df874966d096c6529dbfb9d5  stdin


     out9: 1.86GiB 0:00:38 [49.7MiB/s] [49.7MiB/s] [ <=> ]
      in0: 1.85GiB 0:00:38 [49.4MiB/s] [49.4MiB/s] [============>] 100%            
( pvE 0.1 in0 < "${m3t}" | LC_ALL=C sed 's/.*/\L&/'; )   # BSD-sed



37.94s user 0.86s system 101% cpu 38.318 total
d5e2d8487df1136db7c2334a238755c0  stdin



      in0:  313MiB 0:00:00 [3.06GiB/s] [3.06GiB/s] [=====>] 16% ETA 0:00:00
     out9: 1.85GiB 0:00:11 [ 166MiB/s] [ 166MiB/s] [ <=>]
      in0: 1.85GiB 0:00:00 [3.31GiB/s] [3.31GiB/s] [============>] 100%            
( pvE 0.1 in0 < "${m3t}" | LC_ALL=C python3 -c "print(open(0).read().lower())) 

Python 3.9.12 

9.04s user 2.18s system 98% cpu 11.403 total
7ddc0b5cbcfbbfac3c2b6da6731bd262  stdin

     out9: 2.51MiB 0:00:00 [25.1MiB/s] [25.1MiB/s] [ <=> ]
      in0: 1.85GiB 0:00:11 [ 171MiB/s] [ 171MiB/s] [============>] 100%            
     out9: 1.85GiB 0:00:11 [ 171MiB/s] [ 171MiB/s] [ <=> ]
( pvE 0.1 in0 < "${m3t}" | LC_ALL=C ruby -pe '$_.downcase!'; )


ruby 2.6.8p205 (2021-07-07 revision 67951) [universal.arm64e-darwin21]

10.46s user 1.23s system 105% cpu 11.073 total
85759a34df874966d096c6529dbfb9d5  stdin


      in0: 1.85GiB 0:00:01 [1.01GiB/s] [1.01GiB/s] [============>] 100%            
     out9: 1.85GiB 0:00:01 [1.01GiB/s] [1.01GiB/s] [ <=> ]
( pvE 0.1 in0 < "${m3t}" | LC_ALL=C gtr '[A-Z]' '[a-z]'; )  # GNU-tr


gtr (GNU coreutils) 9.1

1.11s user 1.21s system 124% cpu 1.855 total
85759a34df874966d096c6529dbfb9d5  stdin


     out9: 1.85GiB 0:01:19 [23.7MiB/s] [23.7MiB/s] [ <=> ]
      in0: 1.85GiB 0:01:19 [23.7MiB/s] [23.7MiB/s] [============>] 100%            
( pvE 0.1 in0 < "${m3t}" | LC_ALL=C tr '[A-Z]' '[a-z]'; ) # BSD-tr

78.94s user 1.50s system 100% cpu 1:19.67 total
85759a34df874966d096c6529dbfb9d5  stdin


( time ( pvE0 < "${m3t}" | LC_ALL=C   gdd  conv=lcase ) | pvE9 )  | xxh128sum | lgp3; sleep 3; 
     out9: 0.00 B 0:00:01 [0.00 B/s] [0.00 B/s] [<=> ]
      in0: 1.85GiB 0:00:06 [ 295MiB/s] [ 295MiB/s] [============>] 100%            
     out9: 1.81GiB 0:00:06 [ 392MiB/s] [ 294MiB/s] [ <=>   ]
3874110+1 records in
3874110+1 records out
     out9: 1.85GiB 0:00:06 [ 295MiB/s] [ 295MiB/s] [ <=>  ]
( pvE 0.1 in0 < "${m3t}" | LC_ALL=C gdd conv=lcase; )  # GNU-dd


gdd (coreutils) 9.1

1.93s user 4.35s system 97% cpu 6.413 total
85759a34df874966d096c6529dbfb9d5  stdin



%  ( time ( pvE0 < "${m3t}" | LC_ALL=C   dd  conv=lcase ) | pvE9 )  | xxh128sum | lgp3; sleep 3; 
     out9: 36.9MiB 0:00:00 [ 368MiB/s] [ 368MiB/s] [ <=> ]
      in0: 1.85GiB 0:00:04 [ 393MiB/s] [ 393MiB/s] [============>] 100%            
     out9: 1.85GiB 0:00:04 [ 393MiB/s] [ 393MiB/s] [ <=>   ]
3874110+1 records in
3874110+1 records out
     out9: 1.85GiB 0:00:04 [ 393MiB/s] [ 393MiB/s] [ <=>  ]
( pvE 0.1 in0 < "${m3t}" | LC_ALL=C dd conv=lcase; )  # BSD-dd


1.92s user 4.24s system 127% cpu 4.817 total
85759a34df874966d096c6529dbfb9d5  stdin

————————————————————————————————————————

通过一次加载所有文件,并在单个函数调用中对所有1.85 GB执行tolower(),可以人为地使mawk2比perl5更快::

( time ( pvE0 < "${m3t}" | 

  LC_ALL=C mawk2 '
           BEGIN {            FS = RS = "^$"  } 
             END { print tolower($(ORS = "")) }' 

 ) | pvE9 ) | xxh128sum| lgp3 

      in0: 1.85GiB 0:00:00 [3.35GiB/s] [3.35GiB/s] [============>] 100%            
     out9: 1.85GiB 0:00:02 [ 647MiB/s] [ 647MiB/s] [ <=> ]
( pvE 0.1 in0 < "${m3t}" | LC_ALL=C mawk2 ; )


1.39s user 1.31s system 91% cpu 2.935 total
85759a34df874966d096c6529dbfb9d5  stdin
echo "Hi All" | tr "[:upper:]" "[:lower:]"