Source: https://stackoverflow.com
The Windows FINDSTR command is horribly documented. There is very basic command line help available through
There are many FINDSTR features and limitations that are not even hinted at in the documentation. Nor could they be anticipated without prior knowledge and/or careful experimentation.
So the question is - What are the undocumented FINDSTR features and limitations?
The purpose of this question is to provide a one stop repository of the many undocumented features so that:
A) Developers can take full advantage of the features that are there.
B) Developers don't waste their time wondering why something doesn't work when it seems like it should.
Please make sure you know the existing documentation before responding. If the information is covered by the HELP, then it does not belong here.
Neither is this a place to show interesting uses of FINDSTR. If a logical person could anticipate the behavior of a particular usage of FINDSTR based on the documentation, then it does not belong here.
Along the same lines, if a logical person could anticipate the behavior of a particular usage based on information contained in any existing answers, then again, it does not belong here.
Preface
Much of the information in this answer has been gathered based on experiments run on a Vista machine. Unless explicitly stated otherwise, I have not confirmed whether the information applies to other Windows versions.
FINDSTR output
The documentation never bothers to explain the output of FINDSTR. It alludes to the fact that matching lines are printed, but nothing more.
The format of matching line output is as follows:
filename:lineNumber:lineOffset:text
where
fileName: = The name of the file containing the matching line. The file name is not printed if the request was explicitly for a single file, or if searching piped input or redirected input. When printed, the fileName will always include any path information provided. Additional path information will be added if the
Note - The filename prefix can be avoided when searching multiple files by using the non-standard (and poorly documented) wildcards
lineNumber: = The line number of the matching line represented as a decimal value with 1 representing the 1st line of the input. Only printed if
lineOffset: = The decimal byte offset of the start of the matching line, with 0 representing the 1st character of the 1st line. Only printed if
text = The binary representation of the matching line, including any <CR> and/or <LF>. Nothing is left out of the binary output, such that this example that matches all lines will produce an exact binary copy of the original file.
FINDSTR on XP displays most non-printable control characters from matching lines as dots (periods) on the screen. The following control characters are exceptions; they display as themselves: 0x09 Tab, 0x0A LineFeed, 0x0B Vertical Tab, 0x0C Form Feed, 0x0D Carriage Return.
XP FINDSTR also converts a number of extended ASCII characters to dots as well. The extended ASCII characters that display as dots on XP are the same as those that are transformed when supplied on the command line. See the "Character limits for command line parameters - Extended ASCII transformation" section, later in this post
Control characters and extended ASCII are not converted to dots on XP if the output is piped, redirected to a file, or within a FOR IN() clause.
Vista and Windows 7 always display all characters as themselves, never as dots.
Return Codes (ERRORLEVEL)
Findstr can search data from only one of the following sources:
File name arguments and
Source of search strings (Updated based on tests with Windows 7)
The
File names must not be quoted within the file when using the
File names may contain spaces and other special characters. Most commands require that such file names are quoted. But the FINDSTR
BUG - Short 8.3 filenames can break the
As with all Windows commands, FINDSTR will attempt to match both the long name and the short 8.3 name when looking for files to search. Assume the current folder contains the following non-empty files:
But a bug with the
Each directory searched is treated independently. For example, the
The commands work bug free if the same file names are created on a machine that has NTFS 8.3 name generation disabled. Of course
Not all short names trigger the bug. All instances of bugged behavior I have seen involve an extension that is longer than 3 characters with a short 8.3 name that begins the same as a normal name that does not require an 8.3 name.
The bug has been confirmed on XP, Vista, and Windows 7.
Non-Printable characters and the
The
0-7, 14-25, 27-31.
Put another way, the
Piped and Redirected input may have
If the input is piped in and the last character of the stream is not
The same is true for redirected input on Vista. If the last character of a file used as redirected input is not
FINDSTR hangs on XP and Windows 7 if redirected input does not end with
This is a nasty "feature" on XP and Windows 7. If the last character of a file used as redirected input does not end with
Last line of Piped data may be ignored if it consists of a single character
If the input is piped in and the last line consists of a single character that is not followed by
Example - The first command with a single character and no
Option syntax
Options can be prefixed with either
The following are all equivalent ways of expressing a case insensitive regex search for any line that contains both "hello" and "goodbye" in any order
On Vista the maximum allowed length for a single search string is 511 bytes. If any search string exceeds 511 then the result is a
When doing a regular expression search, the maximum search string length is 254. A regular expression with length between 255 and 511 will result in a
On Windows XP the search string length is apparently shorter. Findstr error: "Search string too long": How to extract and match substring in "for" loop? The XP limit is 127 bytes for both literal and regex searches.
Line Length limits
Files specified as a command line argument or via the /F:FILE option have no known line length limit. Searches were successfully run against a 128MB file that did not contain a single <LF>.
Piped data and Redirected input is limited to 8191 bytes per line. This limit is a "feature" of FINDSTR. It is not inherent to pipes or redirection. FINDSTR using redirected stdin or piped input will never match any line that is >=8k bytes. Lines >= 8k generate an error message to stderr, but ERRORLEVEL is still 0 if the search string is found in at least one line of at least one file.
Default type of search: Literal vs Regular Expression
Recommendation - Always explicitly specify
BUG - Specifying multiple literal search strings can give unreliable results
The following simple FINDSTR example fails to find a match, even though it should.
Based on experiments, FINDSTR may fail if all of the following conditions are met:
For more info see Why doesn't this FINDSTR example with multiple literal search strings find a match?
Standalone quotes and backslashes within a literal search string file specified by /G:file need not be escaped, but they can be.
If the intent is to find \\, then at least the leading backslash must be escaped. Both
If the intent is to find \", then at least the leading backslash must be escaped. Both
Escaping Quote and Backslash within /G:FILE regex search strings
This is the one case where the escape sequences work as expected based on the documentation. Quote is not a regex metacharacter, so it need not be escaped (but can be). Backslash is a regex metacharacter, so it must be escaped.
Character limits for command line parameters - Extended ASCII transformation
The null character (0x00) cannot appear in any string on the command line. Any other single byte character can appear in the string (0x01 - 0xFF). However, FINDSTR converts many extended ASCII characters it finds within command line parameters into other characters. This has a major impact in two ways:
1) Many extended ASCII characters will not match themselves if used as a search string on the command line. This limitation is the same for literal and regex searches. If a search string must contain extended ASCII, then the
2) FINDSTR may fail to find a file if the name contains extended ASCII characters and the file name is specified on the command line. If a file to be searched contains extended ASCII in the name, then the
Here is a complete list of extended ASCII character transformations that FINDSTR performs on command line strings. Each character is represented as the decimal byte code value. The first code represents the character as supplied on the command line, and the second code represents the character it is transformed into. Note - this list was compiled on a U.S machine. I do not know what impact other languages may have on this list.
Character limits for strings found in files specified by /G:FILE and /F:FILE options
The nul (0x00) character can appear in the file, but it functions like the C string terminator. Any characters after a nul character are treated as a different string as if they were on another line.
The
All other single byte characters are included perfectly within a string.
Searching Unicode files
FINDSTR cannot properly search most Unicode (UTF-16, UTF-16LE, UTF-16BE, UTF-32) because it cannot search for nul bytes and Unicode typically contains many nul bytes.
However, the TYPE command converts UTF-16LE with BOM to a single byte character set, so a command like the following will work with UTF-16LE with BOM.
It is possible to search UTF-8 as long as your search string contains only ASCII. However, the console output of any multi-byte UTF-8 characters will not be correct. But if you redirect the output to a file, then the result will be correctly encoded UTF-8. Note that if the UTF-8 file contains a BOM, then the BOM will be considered as part of the first line, which could throw off a search that matches the beginning of a line.
It is possible to search multi-byte UTF-8 characters if you put your search string in a UTF-8 encoded search file (without BOM), and use the /G option.
End Of Line
FINDSTR breaks lines immediately after every <LF>. The presence or absence of <CR> has no impact on line breaks.
Searching across line breaks
As expected, the
Assume TEXT.TXT has these contents (could be Unix or Windows style)
The Windows FINDSTR command is horribly documented. There is very basic command line help available through
FINDSTR /?, or HELP FINDSTR, but it is woefully inadequate. There is a wee bit more documentation online at https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/findstr.There are many FINDSTR features and limitations that are not even hinted at in the documentation. Nor could they be anticipated without prior knowledge and/or careful experimentation.
So the question is - What are the undocumented FINDSTR features and limitations?
The purpose of this question is to provide a one stop repository of the many undocumented features so that:
A) Developers can take full advantage of the features that are there.
B) Developers don't waste their time wondering why something doesn't work when it seems like it should.
Please make sure you know the existing documentation before responding. If the information is covered by the HELP, then it does not belong here.
Neither is this a place to show interesting uses of FINDSTR. If a logical person could anticipate the behavior of a particular usage of FINDSTR based on the documentation, then it does not belong here.
Along the same lines, if a logical person could anticipate the behavior of a particular usage based on information contained in any existing answers, then again, it does not belong here.
Preface
Much of the information in this answer has been gathered based on experiments run on a Vista machine. Unless explicitly stated otherwise, I have not confirmed whether the information applies to other Windows versions.
FINDSTR output
The documentation never bothers to explain the output of FINDSTR. It alludes to the fact that matching lines are printed, but nothing more.
The format of matching line output is as follows:
filename:lineNumber:lineOffset:text
where
fileName: = The name of the file containing the matching line. The file name is not printed if the request was explicitly for a single file, or if searching piped input or redirected input. When printed, the fileName will always include any path information provided. Additional path information will be added if the
/S
option is used. The printed path is always relative to the provided
path, or relative to the current directory if none provided.Note - The filename prefix can be avoided when searching multiple files by using the non-standard (and poorly documented) wildcards
< and >. The exact rules for how these wildcards work can be found here. Finally, you can look at this example of how the non-standard wildcards work with FINDSTR.lineNumber: = The line number of the matching line represented as a decimal value with 1 representing the 1st line of the input. Only printed if
/N option is specified.lineOffset: = The decimal byte offset of the start of the matching line, with 0 representing the 1st character of the 1st line. Only printed if
/O option is specified. This is not the offset of the match within the line. It is the number of bytes from the beginning of the file to the beginning of the line.text = The binary representation of the matching line, including any <CR> and/or <LF>. Nothing is left out of the binary output, such that this example that matches all lines will produce an exact binary copy of the original file.
FINDSTR "^" FILE >FILE_COPY
FINDSTR on XP displays most non-printable control characters from matching lines as dots (periods) on the screen. The following control characters are exceptions; they display as themselves: 0x09 Tab, 0x0A LineFeed, 0x0B Vertical Tab, 0x0C Form Feed, 0x0D Carriage Return.
XP FINDSTR also converts a number of extended ASCII characters to dots as well. The extended ASCII characters that display as dots on XP are the same as those that are transformed when supplied on the command line. See the "Character limits for command line parameters - Extended ASCII transformation" section, later in this post
Control characters and extended ASCII are not converted to dots on XP if the output is piped, redirected to a file, or within a FOR IN() clause.
Vista and Windows 7 always display all characters as themselves, never as dots.
Return Codes (ERRORLEVEL)
- 0 (success)
- Match was found in at least one line of at least one file.
- 1 (failure)
- No match was found in any line of any file.
- Invalid color specified by
/A:xxoption
- 2 (error)
- Incompatible options
/Land/Rboth specified - Missing argument after
/A:,/F:,/C:,/D:, or/G: - File specified by
/F:fileor/G:filenot found
- Incompatible options
- 255 (error)
- Too many regular expression character class terms
see Regex character class term limit and BUG in part 2 of answer
- Too many regular expression character class terms
Findstr can search data from only one of the following sources:
- filenames specified as arguments and/or using the
/F:fileoption. - stdin via redirection
findstr "searchString" <file - data stream from a pipe
type file | findstr "searchString"
File name arguments and
/F:file may be combined. Multiple file name arguments may be used. If multiple /F:file
options are specified, then only the last one is used. Wild cards are
allowed in filename arguments, but not within the file pointed to by /F:file.Source of search strings (Updated based on tests with Windows 7)
The
/G:file and /C:string options may be combined. Multiple /C:string options may be specified. If multiple /G:file options are specified, then only the last one is used. If either /G:file or /C:string is used, then all non-option arguments are assumed to be files to search. If neither /G:file nor /C:string is used, then the first non-option argument is treated as a space delimited list of search terms.File names must not be quoted within the file when using the
/F:FILE option.File names may contain spaces and other special characters. Most commands require that such file names are quoted. But the FINDSTR
/F:files.txt option requires that filenames within files.txt must NOT be quoted. The file will not be found if the name is quoted.BUG - Short 8.3 filenames can break the
/D and /S optionsAs with all Windows commands, FINDSTR will attempt to match both the long name and the short 8.3 name when looking for files to search. Assume the current folder contains the following non-empty files:
b1.txt
b.txt2
c.txt
findstr /m "^" *.txt
b.txt2 matches because the corresponding short name B9F64~1.TXT matches. This is consistent with the behavior of all other Windows commands.But a bug with the
/D and /S options causes the following commands to only find b1.txtfindstr /m /d:. "^" *.txt
findstr /m /s "^" *.txt
b.txt2 from being found, as well as all file names that sort after b.txt2 within the same directory. Additional files that sort before, like a.txt, are found. Additional files that sort later, like d.txt, are missed once the bug has been triggered.Each directory searched is treated independently. For example, the
/S
option would successfully begin searching in a child folder after
failing to find files in the parent, but once the bug causes a short
file name to be missed in the child, then all subsequent files in that
child folder would also be missed.The commands work bug free if the same file names are created on a machine that has NTFS 8.3 name generation disabled. Of course
b.txt2 would not be found, but c.txt would be found properly.Not all short names trigger the bug. All instances of bugged behavior I have seen involve an extension that is longer than 3 characters with a short 8.3 name that begins the same as a normal name that does not require an 8.3 name.
The bug has been confirmed on XP, Vista, and Windows 7.
Non-Printable characters and the
/P optionThe
/P option causes FINDSTR to skip any file that contains any of the following decimal byte codes:0-7, 14-25, 27-31.
Put another way, the
/P option will only skip files that
contain non-printable control characters. Control characters are codes
less than or equal to 31 (0x1F). FINDSTR treats the following control
characters as printable: 8 0x08 backspace
9 0x09 horizontal tab
10 0x0A line feed
11 0x0B vertical tab
12 0x0C form feed
13 0x0D carriage return
26 0x1A substitute (end of text)
/P option to skip the file.Piped and Redirected input may have
<CR><LF> appendedIf the input is piped in and the last character of the stream is not
<LF>, then FINDSTR will automatically append <CR><LF> to the input. This has been confirmed on XP, Vista and Windows 7. (I
used to think that the Windows pipe was responsible for modifying the
input, but I have since discovered that FINDSTR is actually doing the
modification.) The same is true for redirected input on Vista. If the last character of a file used as redirected input is not
<LF>, then FINDSTR will automatically append <CR><LF> to the input. However, XP and Windows 7 do not alter redirected input.FINDSTR hangs on XP and Windows 7 if redirected input does not end with
<LF>This is a nasty "feature" on XP and Windows 7. If the last character of a file used as redirected input does not end with
<LF>, then FINDSTR will hang indefinitely once it reaches the end of the redirected file.Last line of Piped data may be ignored if it consists of a single character
If the input is piped in and the last line consists of a single character that is not followed by
<LF>, then FINDSTR completely ignores the last line.Example - The first command with a single character and no
<LF>
fails to match, but the second command with 2 characters works fine, as
does the third command that has one character with terminating newline.> set /p "=x" <nul | findstr "^"
> set /p "=xx" <nul | findstr "^"
xx
> echo x| findstr "^"
x
Option syntax
Options can be prefixed with either
/ or -
Options may be concatenated after a single / or -.
However, the concatenated option list may contain at most one
multicharacter option such as OFF or F:, and the multi-character option
must be the last option in the list.The following are all equivalent ways of expressing a case insensitive regex search for any line that contains both "hello" and "goodbye" in any order
/i /r /c:"hello.*goodbye" /c:"goodbye.*hello"-i -r -c:"hello.*goodbye" /c:"goodbye.*hello"/irc:"hello.*goodbye" /c:"goodbye.*hello"
On Vista the maximum allowed length for a single search string is 511 bytes. If any search string exceeds 511 then the result is a
FINDSTR: Search string too long. error with ERRORLEVEL 2.When doing a regular expression search, the maximum search string length is 254. A regular expression with length between 255 and 511 will result in a
FINDSTR: Out of memory error with ERRORLEVEL 2. A regular expression length >511 results in the FINDSTR: Search string too long. error.On Windows XP the search string length is apparently shorter. Findstr error: "Search string too long": How to extract and match substring in "for" loop? The XP limit is 127 bytes for both literal and regex searches.
Line Length limits
Files specified as a command line argument or via the /F:FILE option have no known line length limit. Searches were successfully run against a 128MB file that did not contain a single <LF>.
Piped data and Redirected input is limited to 8191 bytes per line. This limit is a "feature" of FINDSTR. It is not inherent to pipes or redirection. FINDSTR using redirected stdin or piped input will never match any line that is >=8k bytes. Lines >= 8k generate an error message to stderr, but ERRORLEVEL is still 0 if the search string is found in at least one line of at least one file.
Default type of search: Literal vs Regular Expression
/C:"string" - The default is /L literal. Explicitly combining the /L option with /C:"string" certainly works but is redundant."string argument" - The default depends on the content of the very first search string. (Remember that <space> is used to delimit search strings.)
If the first search string is a valid regular expression that contains
at least one un-escaped meta-character, then all search strings are
treated as regular expressions. Otherwise all search strings are treated
as literals. For example, "51.4 200" will be treated as two regular expressions because the first string contains an un-escaped dot, whereas "200 51.4" will be treated as two literals because the first string does not contain any meta-characters./G:file - The default depends on the content of the
first non-empty line in the file. If the first search string is a valid
regular expression that contains at least one un-escaped meta-character,
then all search strings are treated as regular expressions. Otherwise
all search strings are treated as literals.Recommendation - Always explicitly specify
/L literal option or /R regular expression option when using "string argument" or /G:file.BUG - Specifying multiple literal search strings can give unreliable results
The following simple FINDSTR example fails to find a match, even though it should.
echo ffffaaa|findstr /l "ffffaaa faffaffddd"
Based on experiments, FINDSTR may fail if all of the following conditions are met:
- The search is using multiple literal search strings
- The search strings are of different lengths
- A short search string has some amount of overlap with a longer search string
- The search is case sensitive (no
/Ioption)
For more info see Why doesn't this FINDSTR example with multiple literal search strings find a match?
Quotes and backslahses within command line arguments - Note:Escaping Quote and Backslash within /G:FILE literal search strings
The information within this highlighted section is not 100% accurate. After I wrote this section, user MC ND pointed me to a reference that documents how the Microsoft C/C++ library parses parameters. It is horrifically complicated, but it appears to accurately predict the backslash and quote rules for FINDSTR command line arguments. I recommend you use the highlighted information below as a guide, but if you want more accurate info, refer to the link.
Escaping Quote within command line search strings
Quotes within command line search strings must be escaped with backslash like\". This is true for both literal and regex search strings. This information has been confirmed on XP, Vista, and Windows 7.
Note: The quote may also need to be escaped for the CMD.EXE parser, but this has nothing to do with FINDSTR. For example, to search for a single quote you could use:
FINDSTR \^" file && echo found || echo not found
Escaping Backslash within command line literal search strings
Backslash in a literal search string can normally be represented as\or as\\. They are typically equivalent. (There may be unusual cases in Vista where the backslash must always be escaped, but I no longer have a Vista machine to test).
But there are some special cases:
When searching for consecutive backslashes, all but the last must be escaped. The last backslash may optionally be escaped.
Searching for one or more backslashes before a quote is bizarre. Logic would suggest that the quote must be escaped, and each of the leading backslashes would need to be escaped, but this does not work! Instead, each of the leading backslashes must be double escaped, and the quote is escaped normally:
\\can be coded as\\\or\\\\\\\can be coded as\\\\\or\\\\\\
As previously noted, one or more escaped quotes may also require escaping with
\"must be coded as\\\\\"\\"must be coded as\\\\\\\\\"^for the CMD parser
The info in this section has been confirmed on XP and Windows 7.
Escaping Backslash within command line regex search strings
- Vista only: Backslash in a regex must be either double escaped like
\\\\, or else single escaped within a character class set like[\\]- XP and Windows 7: Backslash in a regex can always be represented as
[\\]. It can normally be represented as\\. But this never works if the backslash precedes an escaped quote.
One or more backslashes before an escaped quote must either be double escaped, or else coded as[\\]
\"may be coded as\\\\\"or[\\]\"\\"may be coded as\\\\\\\\\"or[\\][\\]\"or\\[\\]\"
Standalone quotes and backslashes within a literal search string file specified by /G:file need not be escaped, but they can be.
" and \" are equivalent.\ and \\ are equivalent.If the intent is to find \\, then at least the leading backslash must be escaped. Both
\\\ and \\\\ work.If the intent is to find \", then at least the leading backslash must be escaped. Both
\\" and \\\" work.Escaping Quote and Backslash within /G:FILE regex search strings
This is the one case where the escape sequences work as expected based on the documentation. Quote is not a regex metacharacter, so it need not be escaped (but can be). Backslash is a regex metacharacter, so it must be escaped.
Character limits for command line parameters - Extended ASCII transformation
The null character (0x00) cannot appear in any string on the command line. Any other single byte character can appear in the string (0x01 - 0xFF). However, FINDSTR converts many extended ASCII characters it finds within command line parameters into other characters. This has a major impact in two ways:
1) Many extended ASCII characters will not match themselves if used as a search string on the command line. This limitation is the same for literal and regex searches. If a search string must contain extended ASCII, then the
/G:FILE option should be used instead.2) FINDSTR may fail to find a file if the name contains extended ASCII characters and the file name is specified on the command line. If a file to be searched contains extended ASCII in the name, then the
/F:FILE option should be used instead.Here is a complete list of extended ASCII character transformations that FINDSTR performs on command line strings. Each character is represented as the decimal byte code value. The first code represents the character as supplied on the command line, and the second code represents the character it is transformed into. Note - this list was compiled on a U.S machine. I do not know what impact other languages may have on this list.
158 treated as 080 199 treated as 221 226 treated as 071
169 treated as 170 200 treated as 043 227 treated as 112
176 treated as 221 201 treated as 043 228 treated as 083
177 treated as 221 202 treated as 045 229 treated as 115
178 treated as 221 203 treated as 045 231 treated as 116
179 treated as 221 204 treated as 221 232 treated as 070
180 treated as 221 205 treated as 045 233 treated as 084
181 treated as 221 206 treated as 043 234 treated as 079
182 treated as 221 207 treated as 045 235 treated as 100
183 treated as 043 208 treated as 045 236 treated as 056
184 treated as 043 209 treated as 045 237 treated as 102
185 treated as 221 210 treated as 045 238 treated as 101
186 treated as 221 211 treated as 043 239 treated as 110
187 treated as 043 212 treated as 043 240 treated as 061
188 treated as 043 213 treated as 043 242 treated as 061
189 treated as 043 214 treated as 043 243 treated as 061
190 treated as 043 215 treated as 043 244 treated as 040
191 treated as 043 216 treated as 043 245 treated as 041
192 treated as 043 217 treated as 043 247 treated as 126
193 treated as 045 218 treated as 043 249 treated as 250
194 treated as 045 219 treated as 221 251 treated as 118
195 treated as 043 220 treated as 095 252 treated as 110
196 treated as 045 222 treated as 221 254 treated as 221
197 treated as 043 223 treated as 095
198 treated as 221 224 treated as 097
<CR> and <LF>. The easiest way to include odd characters like <CR> and <LF> is to get them into an environment variable and use delayed expansion within the command line argument.Character limits for strings found in files specified by /G:FILE and /F:FILE options
The nul (0x00) character can appear in the file, but it functions like the C string terminator. Any characters after a nul character are treated as a different string as if they were on another line.
The
<CR> and <LF> characters are treated as line terminators that terminate a string, and are not included in the string.All other single byte characters are included perfectly within a string.
Searching Unicode files
FINDSTR cannot properly search most Unicode (UTF-16, UTF-16LE, UTF-16BE, UTF-32) because it cannot search for nul bytes and Unicode typically contains many nul bytes.
However, the TYPE command converts UTF-16LE with BOM to a single byte character set, so a command like the following will work with UTF-16LE with BOM.
type unicode.txt|findstr "search"
? characters.It is possible to search UTF-8 as long as your search string contains only ASCII. However, the console output of any multi-byte UTF-8 characters will not be correct. But if you redirect the output to a file, then the result will be correctly encoded UTF-8. Note that if the UTF-8 file contains a BOM, then the BOM will be considered as part of the first line, which could throw off a search that matches the beginning of a line.
It is possible to search multi-byte UTF-8 characters if you put your search string in a UTF-8 encoded search file (without BOM), and use the /G option.
End Of Line
FINDSTR breaks lines immediately after every <LF>. The presence or absence of <CR> has no impact on line breaks.
Searching across line breaks
As expected, the
. regex metacharacter will not match
<CR> or <LF>. But it is possible to search across a line
break using a command line search string. Both the <CR> and
<LF> characters must be matched explicitly. If a multi-line match
is found, only the 1st line of the match is printed. FINDSTR then
doubles back to the 2nd line in the source and begins the search all
over again - sort of a "look ahead" type feature.Assume TEXT.TXT has these contents (could be Unix or Windows style)
A
A
A
B
A
A
@echo off
setlocal
::Define LF variable containing a linefeed (0x0A)
set LF=^
::Above 2 blank lines are critical - do not remove
::Define CR variable containing a carriage return (0x0D)
for /f %%a in ('copy /Z "%~dpf0" nul') do set "CR=%%a"
setlocal enableDelayedExpansion
::regex "!CR!*!LF!" will match both Unix and Windows style End-Of-Line
findstr /n /r /c:"A!CR!*!LF!A" TEST.TXT
1:A
2:A
5:A
[<TAB>-<0x0B>]matches <LF>, but it also matches <TAB> and <0x0B>[<0x0C>-!]matches <CR>, but it also matches <0x0C> and !
Note - the above are symbolic representations of the regex byte stream since I can't graphically represent the characters.
Limited Regular Expressions (regex) Support
FINDSTR support for regular expressions is extremely limited. If it is not in the HELP documentation, it is not supported.
Beyond that, the regex expressions that are supported are implemented in a completely non-standard manner, such that results can be different then would be expected coming from something like grep or perl.
Regex Line Position anchors ^ and $
^matches beginning of input stream as well as any position immediately following a <LF>. Since FINDSTR also breaks lines after <LF>, a simple regex of "^" will always match all lines within a file, even a binary file.
$matches any position immediately preceding a <CR>. This means that a regex search string containing$will never match any lines within a Unix style text file, nor will it match the last line of a Windows text file if it is missing the EOL marker of <CR><LF>.
Note - As previously discussed, piped and redirected input to FINDSTR may have<CR><LF>appended that is not in the source. Obviously this can impact a regex search that uses$.
Any search string with characters before^or after$will always fail to find a match.
Positional Options /B /E /X
The positional options work the same as^and$, except they also work for literal search strings.
/B functions the same as^at the start of a regex search string.
/E functions the same as$at the end of a regex search string.
/X functions the same as having both^at the beginning and$at the end of a regex search string.
Regex word boundary
\<must be the very first term in the regex. The regex will not match anything if any other characters precede it.\<corresponds to either the very beginning of the input, the beginning of a line (the position immediately following a <LF>), or the position immediately following any "non-word" character. The next character need not be a "word" character.
\>must be the very last term in the regex. The regex will not match anything if any other characters follow it.\>corresponds to either the end of input, the position immediately prior to a <CR>, or the position immediately preceding any "non-word" character. The preceding character need not be a "word" character.
Here is a complete list of "non-word" characters, represented as the decimal byte code. Note - this list was compiled on a U.S machine. I do not know what impact other languages may have on this list.
Regex character class ranges [x-y]001 028 063 179 204 230 002 029 064 180 205 231 003 030 091 181 206 232 004 031 092 182 207 233 005 032 093 183 208 234 006 033 094 184 209 235 007 034 096 185 210 236 008 035 123 186 211 237 009 036 124 187 212 238 011 037 125 188 213 239 012 038 126 189 214 240 014 039 127 190 215 241 015 040 155 191 216 242 016 041 156 192 217 243 017 042 157 193 218 244 018 043 158 194 219 245 019 044 168 195 220 246 020 045 169 196 221 247 021 046 170 197 222 248 022 047 173 198 223 249 023 058 174 199 224 250 024 059 175 200 226 251 025 060 176 201 227 254 026 061 177 202 228 255 027 062 178 203 229
Character class ranges do not work as expected. See this question: Why does findstr not handle case properly (in some circumstances)?, along with this answer: https://stackoverflow.com/a/8767815/1012053.
The problem is FINDSTR does not collate the characters by their byte code value (commonly thought of as the ASCII code, but ASCII is only defined from 0x00 - 0x7F). Most regex implementations would treat [A-Z] as all upper case English capital letters. But FINDSTR uses a collation sequence that roughly corresponds to how SORT works. So [A-Z] includes the complete English alphabet, both upper and lower case (except for "a"), as well as non-English alpha characters with diacriticals.
- Regex character class term limit and BUG
Not only is FINDSTR limited to a maximum of 15 character class terms within a regex, it fails to properly handle an attempt to exceed the limit. Using 16 or more character class terms results in an interactive Windows pop up stating "Find String (QGREP) Utility has encountered a problem and needs to close. We are sorry for the inconvenience." The message text varies slightly depending on the Windows version. Here is one example of a FINDSTR that will fail:
This bug was reported by DosTips user Judago here. It has been confirmed on XP, Vista, and Windows 7.echo 01234567890123456|findstr [0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]
Regex searches fail (and may hang indefinitely) if they include byte code 0xFF (decimal 255)
Any regex search that includes byte code 0xFF (decimal 255) will fail. It fails if byte code 0xFF is included directly, or if it is implicitly included within a character class range. Remember that FINDSTR character class ranges do not collate characters based on the byte code value. Character<0xFF>appears relatively early in the collation sequence between the<space>and<tab>characters. So any character class range that includes both<space>and<tab>will fail.
The exact behavior changes slightly depending on the Windows version. Windows 7 hangs indefinitely if 0xFF is included. XP doesn't hang, but it always fails to find a match, and occasionally prints the following error message - "The process tried to write to a nonexistent pipe."
I no longer have access to a Vista machine, so I haven't been able to test on Vista.
Regex bug:.and[^anySet]can match End-Of-File
The regex.meta-character should only match any character other than<CR>or<LF>. There is a bug that allows it to match the End-Of-File if the last line in the file is not terminated by<CR>or<LF>. However, the.will not match an empty file.
For example, a file named "test.txt" containing a single line ofx, without terminating<CR>or<LF>, will match the following:
This bug has been confirmed on XP and Win7.findstr /r x......... test.txt
The same seems to be true for negative character sets. Something like[^abc]will match End-Of-File. Positive character sets like[abc]seem to work fine. I have only tested this on Win7.
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