FOR: Runs a specified command for each file in a set of files.
The command: "FOR" is on Windows 11, 10, .. available
"FOR" Excerpt from Microsoft Windows Help
Microsoft Windows [Version 10.0.19045.3693]
(c) Copyright 1985-2023 Microsoft Corp.
C:\\WINDOWS>
Runs a specified command for each file in a set of files.
FOR %variable IN (set) DO command [command-parameters]
%variable Specifies a single letter replaceable parameter.
(set) Specifies a set of one or more files. Wildcards may be used.
command Specifies the command to carry out for each file.
command-parameters
Specifies parameters or switches for the specified command.
To use the FOR command in a batch program, specify %%variable instead
of %variable. Variable names are case sensitive, so %i is different
from %I.
If Command Extensions are enabled, the following additional
forms of the FOR command are supported:
FOR /D %variable IN (set) DO command [command-parameters]
If set contains wildcards, then specifies to match against directory
names instead of file names.
FOR /R [[drive:]path] %variable IN (set) DO command [command-parameters]
Walks the directory tree rooted at [drive:]path, executing the FOR
statement in each directory of the tree. If no directory
specification is specified after /R then the current directory is
assumed. If set is just a single period (.) character then it
will just enumerate the directory tree.
FOR /L %variable IN (start,step,end) DO command [command-parameters]
The set is a sequence of numbers from start to end, by step amount.
So (1,1,5) would generate the sequence 1 2 3 4 5 and (5,-1,1) would
generate the sequence (5 4 3 2 1)
FOR /F ["options"] %variable IN (file-set) DO command [command-parameters]
FOR /F ["options"] %variable IN ("string") DO command [command-parameters]
FOR /F ["options"] %variable IN ('command') DO command [command-parameters]
or, if usebackq option present:
FOR /F ["options"] %variable IN (file-set) DO command [command-parameters]
FOR /F ["options"] %variable IN ('string') DO command [command-parameters]
FOR /F ["options"] %variable IN (`command`) DO command [command-parameters]
filenameset is one or more file names. Each file is opened, read
and processed before going on to the next file in filenameset.
Processing consists of reading in the file, breaking it up into
individual lines of text and then parsing each line into zero or
more tokens. The body of the for loop is then called with the
variable value(s) set to the found token string(s). By default, /F
passes the first blank separated token from each line of each file.
Blank lines are skipped. You can override the default parsing
behavior by specifying the optional "options" parameter. This
is a quoted string which contains one or more keywords to specify
different parsing options. The keywords are:
eol=c - specifies an end of line comment character
(just one)
skip=n - specifies the number of lines to skip at the
beginning of the file.
delims=xxx - specifies a delimiter set. This replaces the
default delimiter set of space and tab.
tokens=x,y,m-n - specifies which tokens from each line are to
be passed to the for body for each iteration.
This will cause additional variable names to
be allocated. The m-n form is a range,
specifying the mth through the nth tokens. If
the last character in the tokens= string is an
asterisk, then an additional variable is
allocated and receives the remaining text on
the line after the last token parsed.
usebackq - specifies that the new semantics are in force,
where a back quoted string is executed as a
command and a single quoted string is a
literal string command and allows the use of
double quotes to quote file names in
filenameset.
Some examples might help:
FOR /F "eol=; tokens=2,3* delims=, " %i in (myfile.txt) do @echo %i %j %k
would parse each line in myfile.txt, ignoring lines that begin with
a semicolon, passing the 2nd and 3rd token from each line to the for
body, with tokens delimited by commas and/or spaces. Notice the for
body statements reference %i to get the 2nd token, %j to get the
3rd token, and %k to get all remaining tokens after the 3rd. For
file names that contain spaces, you need to quote the filenames with
double quotes. In order to use double quotes in this manner, you also
need to use the usebackq option, otherwise the double quotes will be
interpreted as defining a literal string to parse.
%i is explicitly declared in the for statement and the %j and %k
are implicitly declared via the tokens= option. You can specify up
to 26 tokens via the tokens= line, provided it does not cause an
attempt to declare a variable higher than the letter 'z' or 'Z'.
Remember, FOR variables are single-letter, case sensitive, global,
and you can't have more than 52 total active at any one time.
You can also use the FOR /F parsing logic on an immediate string, by
making the filenameset between the parenthesis a quoted string,
using single quote characters. It will be treated as a single line
of input from a file and parsed.
Finally, you can use the FOR /F command to parse the output of a
command. You do this by making the filenameset between the
parenthesis a back quoted string. It will be treated as a command
line, which is passed to a child CMD.EXE and the output is captured
into memory and parsed as if it was a file. So the following
example:
FOR /F "usebackq delims==" %i IN (`set`) DO @echo %i
would enumerate the environment variable names in the current
environment.
In addition, substitution of FOR variable references has been enhanced.
You can now use the following optional syntax:
%~I - expands %I removing any surrounding quotes (")
%~fI - expands %I to a fully qualified path name
%~dI - expands %I to a drive letter only
%~pI - expands %I to a path only
%~nI - expands %I to a file name only
%~xI - expands %I to a file extension only
%~sI - expanded path contains short names only
%~aI - expands %I to file attributes of file
%~tI - expands %I to date/time of file
%~zI - expands %I to size of file
%~$PATH:I - searches the directories listed in the PATH
environment variable and expands %I to the
fully qualified name of the first one found.
If the environment variable name is not
defined or the file is not found by the
search, then this modifier expands to the
empty string
The modifiers can be combined to get compound results:
%~dpI - expands %I to a drive letter and path only
%~nxI - expands %I to a file name and extension only
%~fsI - expands %I to a full path name with short names only
%~dp$PATH:I - searches the directories listed in the PATH
environment variable for %I and expands to the
drive letter and path of the first one found.
%~ftzaI - expands %I to a DIR like output line
In the above examples %I and PATH can be replaced by other valid
values. The %~ syntax is terminated by a valid FOR variable name.
Picking upper case variable names like %I makes it more readable and
avoids confusion with the modifiers, which are not case sensitive.
The examples for the command "FOR"
The
`FOR` command in Windows Command Prompt is used to loop in batch files. Here are some examples:
Example 1: Looping through files in a directory:
FOR %G IN (directory\*) DO ECHO %G
Description: This command prints the name of each file in the specified directory.
Example 2: Looping through files with a specific file extension:
FOR %G IN (directory\*.txt) DO ECHO %G
Description: Prints the name of each text file in the specified directory.
Example 3: Iterating through files recursively in subdirectories:
FOR /R directory %G IN (*.txt) DO ECHO %G
Description: Recursively traverses all subdirectories of the specified directory and prints the name of each text file.
Example 4: Looping through numbers in a specific range:
FOR /L %G IN (1,1,10) DO ECHO %G
Description: Outputs the numbers from 1 to 10.
Example 5: Looping through characters in a string:
FOR %G IN ("Hello") DO ECHO %G
Description: Prints each letter of the word
"Hello".
Example 6: Looping through file contents line by line:
FOR /F "tokens=*" %G IN (File.txt) DO ECHO %G
Description: Iterates through the lines of the file
"File.txt" and outputs each line.
Example 7: Iterating through environment variables:
FOR %G IN (%PATH%) DO ECHO %G
Description: Iterates through the paths in the
`PATH` environment variable and prints each path.
Example 8: Using `SET` in a loop:
FOR %G IN (1 2 3) DO SET /A Number=%G * 2 & ECHO Double %G is %Number%
Description: Sets a variable
`number` to twice the current number in the loop and prints this.
Example 9: Iterating through subdirectories and files:
FOR /R %G IN (*) DO ECHO %G
Description: Recursively traverses all subdirectories and files in the current directory.
Example 10: Nested Loops:
FOR %G IN (1 2) DO FOR %H IN (AB) DO ECHO %G%H
Description: Nests two loops and prints all combinations of %G and %H.
Please note that in batch files,
`%` should be replaced with
`%%`. For example:
`FOR %G IN (...) DO ECHO %%G`. Only one percent sign is used in the direct prompt (
`%`).
Important information, tips for the "FOR" command
There are a few important points to note when using the
`FOR` command in the Windows Command Prompt:
1.
Syntax in Batch Files: When using the
`FOR` command in a batch file, you must replace
`%` with
`%%`. For example:
`FOR %%G IN (...) DO ECHO %%G`.
2.
Use of Variables: Typically, you use variables (e.g.,
`%%G`) in the
`FOR` loop to store values. Note that the variables cannot access the assigned values ??outside the loop.
SET variable=initial value
FOR %%G IN (Value1 Value2) DO SET Variable=%%G
ECHO %Variable%
Here
`%Variable%` will keep the value
"Initial Value" because the
`SET` statement is executed in a separate
`FOR` loop.
3.
Spaces in paths or filenames: If paths or filenames contain spaces, the path or filename should be enclosed in quotation marks to ensure that they are interpreted correctly.
FOR %%G IN ("Directory with spaces\File with spaces.txt") DO ECHO %%G
4.
Options for the `FOR /F` loop: If you use
`FOR` in conjunction with the
`/F` option (e.g.,
`FOR /F "tokens=*" %%G IN ( File.txt) DO ECHO %%G`), you need to carefully adjust the syntax for the
`tokens` and
`delims` options to get the desired results.
5.
Nested Loops: With nested loops, you must pay attention to the correct use of
`%` or
`%%` to ensure that the variables are referenced in the correct loop.
FOR %%G IN (1 2) DO (
ECHO Outer loop: %%G
FOR %%H IN (AB) DO ECHO Inner loop: %%H
)
6.
End of file lines in `FOR /F`: When you use
`FOR /F` to loop through lines in a file, by default each line up to the first space or tab is considered a token. You can customize this with the
`delims` option.
FOR /F "tokens=* delims=" %%G IN (file.txt) DO ECHO %%G
7.
Date and time variable options: When using the
`%DATE%` or
`%TIME%` variables in a
`FOR` loop, you should pay attention to the regional setting of the system, as the format may vary.
8.
Iterating through files with UTF-8 encoding: The
`FOR /F` command may have difficulty traversing files with UTF-8 encoding. In such cases it might be better to use other tools like
`FINDSTR`.
It is important to consider the specific requirements of your use case and adjust the 'FOR' loop accordingly. You can type
`FOR /?` in the command prompt to see full help and all available options.
