How do I grep for all non-ASCII characters?

You can use the command:

grep --color='auto' -P -n "[\x80-\xFF]" file.xml

This will give you the line number, and will highlight non-ascii chars in red.

In some systems, depending on your settings, the above will not work, so you can grep by the inverse

grep --color='auto' -P -n "[^\x00-\x7F]" file.xml

Note also, that the important bit is the -P flag which equates to --perl-regexp: so it will interpret your pattern as a Perl regular expression. It also says that

this is highly experimental and grep -P may warn of unimplemented features.

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Instead of making assumptions about the byte range of non-ASCII characters, as most of the above solutions do, it's slightly better IMO to be explicit about the actual byte range of ASCII characters instead.

So the first solution for instance would become:

grep --color='auto' -P -n '[^\x00-\x7F]' file.xml

(which basically greps for any character outside of the hexadecimal ASCII range: from \x00 up to \x7F)

On Mountain Lion that won't work (due to the lack of PCRE support in BSD grep), but with pcre installed via Homebrew, the following will work just as well:

pcregrep --color='auto' -n '[^\x00-\x7F]' file.xml

Any pros or cons that anyone can think off?

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The following works for me:

grep -P "[\x80-\xFF]" file.xml

Non-ASCII characters start at 0x80 and go to 0xFF when looking at bytes. Grep (and family) don't do Unicode processing to merge multi-byte characters into a single entity for regex matching as you seem to want. The -P option in my grep allows the use of \xdd escapes in character classes to accomplish what you want.

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The easy way is to define a non-ASCII character... as a character that is not an ASCII character.

LC_ALL=C grep '[^ -~]' file.xml

Add a tab after the ^ if necessary.

Setting LC_COLLATE=C avoids nasty surprises about the meaning of character ranges in many locales. Setting LC_CTYPE=C is necessary to match single-byte characters — otherwise the command would miss invalid byte sequences in the current encoding. Setting LC_ALL=C avoids locale-dependent effects altogether.

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In perl

perl -ane '{ if(m/[[:^ascii:]]/) { print  } }' fileName > newFile

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Here is another variant I found that produced completely different results from the grep search for [\x80-\xFF] in the accepted answer. Perhaps it will be useful to someone to find additional non-ascii characters:

grep --color='auto' -P -n "[^[:ascii:]]" myfile.txt

Note: my computer's grep (a Mac) did not have -P option, so I did brew install grep and started the call above with ggrep instead of grep.

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Searching for non-printable chars. TLDR; Executive Summary

search for control chars AND extended unicode locale setting e.g. LC_ALL=C needed to make grep do what you might expect with extended unicode

SO the preferred non-ascii char finders:

$ perl -ne 'print "$. $_" if m/[\x00-\x08\x0E-\x1F\x80-\xFF]/' notes_unicode_emoji_test

as in top answer, the inverse grep:

$ grep --color='auto' -P -n "[^\x00-\x7F]" notes_unicode_emoji_test

as in top answer but WITH LC_ALL=C:

$ LC_ALL=C grep --color='auto' -P -n "[\x80-\xFF]" notes_unicode_emoji_test

. . more . . excruciating detail on this: . . .

I agree with Harvey above buried in the comments, it is often more useful to search for non-printable characters OR it is easy to think non-ASCII when you really should be thinking non-printable. Harvey suggests "use this: "[^\n -~]". Add \r for DOS text files. That translates to "[^\x0A\x020-\x07E]" and add \x0D for CR"

Also, adding -c (show count of patterns matched) to grep is useful when searching for non-printable chars as the strings matched can mess up terminal.

I found adding range 0-8 and 0x0e-0x1f (to the 0x80-0xff range) is a useful pattern. This excludes the TAB, CR and LF and one or two more uncommon printable chars. So IMHO a quite a useful (albeit crude) grep pattern is THIS one:

grep -c -P -n "[\x00-\x08\x0E-\x1F\x80-\xFF]" *

ACTUALLY, generally you will need to do this:

LC_ALL=C grep -c -P -n "[\x00-\x08\x0E-\x1F\x80-\xFF]" *

breakdown:

LC_ALL=C - set locale to C, otherwise many extended chars will not match (even though they look like they are encoded > 0x80)
\x00-\x08 - non-printable control chars 0 - 7 decimal
\x0E-\x1F - more non-printable control chars 14 - 31 decimal
\x80-1xFF - non-printable chars > 128 decimal
-c - print count of matching lines instead of lines
-P - perl style regexps

Instead of -c you may prefer to use -n (and optionally -b) or -l
-n, --line-number
-b, --byte-offset
-l, --files-with-matches

E.g. practical example of use find to grep all files under current directory:

LC_ALL=C find . -type f -exec grep -c -P -n "[\x00-\x08\x0E-\x1F\x80-\xFF]" {} + 

You may wish to adjust the grep at times. e.g. BS(0x08 - backspace) char used in some printable files or to exclude VT(0x0B - vertical tab). The BEL(0x07) and ESC(0x1B) chars can also be deemed printable in some cases.

Non-Printable ASCII Chars ** marks PRINTABLE but CONTROL chars that is useful to exclude sometimes Dec Hex Ctrl Char description Dec Hex Ctrl Char description 0 00 ^@ NULL 16 10 ^P DATA LINK ESCAPE (DLE) 1 01 ^A START OF HEADING (SOH) 17 11 ^Q DEVICE CONTROL 1 (DC1) 2 02 ^B START OF TEXT (STX) 18 12 ^R DEVICE CONTROL 2 (DC2) 3 03 ^C END OF TEXT (ETX) 19 13 ^S DEVICE CONTROL 3 (DC3) 4 04 ^D END OF TRANSMISSION (EOT) 20 14 ^T DEVICE CONTROL 4 (DC4) 5 05 ^E END OF QUERY (ENQ) 21 15 ^U NEGATIVE ACKNOWLEDGEMENT (NAK) 6 06 ^F ACKNOWLEDGE (ACK) 22 16 ^V SYNCHRONIZE (SYN) 7 07 ^G BEEP (BEL) 23 17 ^W END OF TRANSMISSION BLOCK (ETB) 8 08 ^H BACKSPACE (BS)** 24 18 ^X CANCEL (CAN) 9 09 ^I HORIZONTAL TAB (HT)** 25 19 ^Y END OF MEDIUM (EM) 10 0A ^J LINE FEED (LF)** 26 1A ^Z SUBSTITUTE (SUB) 11 0B ^K VERTICAL TAB (VT)** 27 1B ^[ ESCAPE (ESC) 12 0C ^L FF (FORM FEED)** 28 1C ^\ FILE SEPARATOR (FS) RIGHT ARROW 13 0D ^M CR (CARRIAGE RETURN)** 29 1D ^] GROUP SEPARATOR (GS) LEFT ARROW 14 0E ^N SO (SHIFT OUT) 30 1E ^^ RECORD SEPARATOR (RS) UP ARROW 15 0F ^O SI (SHIFT IN) 31 1F ^_ UNIT SEPARATOR (US) DOWN ARROW

UPDATE: I had to revisit this recently. And, YYMV depending on terminal settings/solar weather forecast BUT . . I noticed that grep was not finding many unicode or extended characters. Even though intuitively they should match the range 0x80 to 0xff, 3 and 4 byte unicode characters were not matched. ??? Can anyone explain this? YES. @frabjous asked and @calandoa explained that LC_ALL=C should be used to set locale for the command to make grep match.

e.g. my locale LC_ALL= empty

$ locale
LANG=en_IE.UTF-8
LC_CTYPE="en_IE.UTF-8"
.
.
LC_ALL=

grep with LC_ALL= empty matches 2 byte encoded chars but not 3 and 4 byte encoded:

$ grep -P -n "[\x00-\x08\x0E-\x1F\x80-\xFF]" notes_unicode_emoji_test
5:© copyright c2a9
7:call  underscore c2a0
9:CTRL
31:5 © copyright
32:7 call  underscore

grep with LC_ALL=C does seem to match all extended characters that you would want:

$ LC_ALL=C grep --color='auto' -P -n "[\x80-\xFF]" notes_unicode_emoji_test  
1:���� unicode dashes e28090
3:��� Heart With Arrow Emoji - Emojipedia == UTF8? f09f9298
5:� copyright c2a9
7:call� underscore c2a0
11:LIVE��E! ���������� ���� ���������� ���� �� �� ���� ����  YEOW, mix of japanese and chars from other e38182 e38184 . . e0a487
29:1 ���� unicode dashes
30:3 ��� Heart With Arrow Emoji - Emojipedia == UTF8 e28090
31:5 � copyright
32:7 call� underscore
33:11 LIVE��E! ���������� ���� ���������� ���� �� �� ���� ����  YEOW, mix of japanese and chars from other
34:52 LIVE��E! ���������� ���� ���������� ���� �� �� ���� ����  YEOW, mix of japanese and chars from other
81:LIVE��E! ���������� ���� ���������� ���� �� �� ���� ����  YEOW, mix of japanese and chars from other

THIS perl match (partially found elsewhere on stackoverflow) OR the inverse grep on the top answer DO seem to find ALL the ~weird~ and ~wonderful~ "non-ascii" characters without setting locale:

$ grep --color='auto' -P -n "[^\x00-\x7F]" notes_unicode_emoji_test

$ perl -ne 'print "$. $_" if m/[\x00-\x08\x0E-\x1F\x80-\xFF]/' notes_unicode_emoji_test  

1 ‐‐ unicode dashes e28090
3 💘 Heart With Arrow Emoji - Emojipedia == UTF8? f09f9298
5 © copyright c2a9
7 call  underscore c2a0
9 CTRL-H CHARS URK URK URK 
11 LIVE‐E! あいうえお かが アイウエオ カガ ᚊ ᚋ ซฌ आइ  YEOW, mix of japanese and chars from other e38182 e38184 . . e0a487
29 1 ‐‐ unicode dashes
30 3 💘 Heart With Arrow Emoji - Emojipedia == UTF8 e28090
31 5 © copyright
32 7 call  underscore
33 11 LIVE‐E! あいうえお かが アイウエオ カガ ᚊ ᚋ ซฌ आइ  YEOW, mix of japanese and chars from other
34 52 LIVE‐E! あいうえお かが アイウエオ カガ ᚊ ᚋ ซฌ आइ  YEOW, mix of japanese and chars from other
73 LIVE‐E! あいうえお かが アイウエオ カガ ᚊ ᚋ ซฌ आइ  YEOW, mix of japanese and chars from other

SO the preferred non-ascii char finders:

$ perl -ne 'print "$. $_" if m/[\x00-\x08\x0E-\x1F\x80-\xFF]/' notes_unicode_emoji_test

as in top answer, the inverse grep:

$ grep --color='auto' -P -n "[^\x00-\x7F]" notes_unicode_emoji_test

as in top answer but WITH LC_ALL=C:

$ LC_ALL=C grep --color='auto' -P -n "[\x80-\xFF]" notes_unicode_emoji_test

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The following code works:

find /tmp | perl -ne 'print if /[^[:ascii:]]/'

Replace /tmp with the name of the directory you want to search through.

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This method should work with any POSIX-compliant version of awk and iconv. We can take advantage of file and tr as well.

curl is not POSIX, of course.

Solutions above may be better in some cases, but they seem to depend on GNU/Linux implementations or additional tools.

Get a sample file:

$ curl -Ls http://gutenberg.org/files/84/84-0.txt

$ file 84-0.txt

84-0.txt: UTF-8 Unicode (with BOM) text, with CRLF line terminators

Search for UTF-8 characters:

$ awk '/[\x80-\xFF]/ { print }' 84-0.txt

or non-ASCII

$ awk '/[^[:ascii:]]/ { print }' 84-0.txt

Convert UTF-8 to ASCII, removing problematic characters:

$ iconv -c -t ASCII 84-0.txt > 84-ascii.txt

Check it:

$ file 84-ascii.txt

84-ascii.txt: ASCII text, with CRLF line terminators

Tweak it:

$ tr -d '\015' < 84-ascii.txt | file -

/dev/stdin: ASCII text

YMMV

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Strangely, I had to do this today! I ended up using Perl because I couldn't get grep/egrep to work (even in -P mode). Something like:

cat blah | perl -en '/\xCA\xFE\xBA\xBE/ && print "found"'

For unicode characters (like \u2212 in example below) use this:

find . ... -exec perl -CA -e '$ARGV = @ARGV[0]; open IN, $ARGV; binmode(IN, ":utf8"); binmode(STDOUT, ":utf8"); while (<IN>) { next unless /\N{U+2212}/; print "$ARGV: $&: $_"; exit }' '{}' \;

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It could be interesting to know how to search for one unicode character. This command can help. You only need to know the code in UTF8

grep -v $'\u200d'

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Finding all non-ascii characters gives the impression that one is either looking for unicode strings or intends to strip said characters individually.

For the former, try one of these (variable file is used for automation):

 file=file.txt ; LC_ALL=C grep -Piao '[\x80-\xFF\x20]{7,}' $file | iconv -f $(uchardet $file) -t utf-8

 file=file.txt ; pcregrep -iao '[\x80-\xFF\x20]{7,}' $file | iconv -f $(uchardet $file) -t utf-8

 file=file.txt ; pcregrep -iao '[^\x00-\x19\x21-\x7F]{7,}' $file | iconv -f $(uchardet $file) -t utf-8

Vanilla grep doesn't work correctly without LC_ALL=C as noted in the previous answers.

ASCII range is x00-x7F, space is x20, since strings have spaces the negative range omits it.

Non-ASCII range is x80-xFF, since strings have spaces the positive range adds it.

String is presumed to be at least 7 consecutive characters within the range. {7,}.

For shell readable output, uchardet $file returns a guess of the file encoding which is passed to iconv for automatic interpolation.

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if you're trying to grab/grep UTF8-compliant multibyte-characters, use this :

(                     [\302-\337][\200-\277]|
                [\340][\240-\277][\200-\277]|
                [\355][\200-\237][\200-\277]|
  [\341-\354\356-\357][\200-\277][\200-\277]|
     [\360][\220-\277][\200-\277][\200-\277]|
[\361-\363][\200-\277][\200-\277][\200-\277]|
     [\364][\200-\217][\200-\277][\200-\277]  ) 

 * please delete all newlines, spaces, or tabs in between (..)

 * feel free to use bracket ranges {1,3} etc to optimize
   the redundant listings of [\200-\277]. but don't change that
   [\200-\277]+, as that might result in invalid encodings 
    due to either insufficient or too many continuation bytes

 * although some historical UTF-8 references considers 5- and 
   6-byte encodings to be valid, as of Unicode 13 they only
   consider up to 4-bytes

I've tested this string even against random binary files, and it would report the same multi-byte character count as gnu-wc.

Add in another [\000-\177]| at the front just after ( of that if you need full UTF8 matching string.

This regex is truly hideous yes, but it's also POSIX-compliant, cross-language and cross-platform compatible (doesn't depend on any special regex notation, (should be) fully UTF-8 compliant (Unicode 13), and completely independent of locale-setting.

if you're running grep with this, please use grep -P

If you just need the other bytes, then others have suggested already.

if you need the 11,172 characters of NFC-composed korean hangul it's

(([\352][\260-\277]|[\353\354][\200-\277]|
 [\355][\200-\235])[\200-\277]|[\355][\236][\200-\243])

and if you need Japanese hiragana+katakana, it's

([\343]([\201-\203][\200-\277]|[\207][\260-\277]))

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