Loop command: against a set of files - conditionally perform a command against each item.
Syntax FOR /F ["options"] %%parameter IN (filenameset) DO command FOR /F ["options"] %%parameter IN ("Text string to process") DO command Key options: delims=xxx The delimiter character(s) (default = a space) skip=n A number of lines to skip at the beginning of the file. (default = 0) eol=; Character at the start of each line to indicate a comment The default is a semicolon ; tokens=n Specifies which numbered items to read from each line (default = 1) usebackq Specify `back quotes`: - Use double quotes to quote long file names in filenameset. - Use single quotes for 'Text string to process' (useful if the text string contains double quotes) Filenameset A set of one or more files. Wildcards may be used. If (filenameset) is a period character (.) then FOR will loop through every file in the folder.
command The command to carry out, including any command-line parameters. %%parameter A replaceable parameter: in a batch file use %%G (on the command line %G)
FOR /F processing of a text file consists of reading the file, one line of text at a time and then breaking the line up into individual items of data called 'tokens'. The DO command is then executed with the parameter(s) set to the token(s) found.
By default, /F breaks up the line at each blank space " ", and any blank lines are skipped, this default parsing behavior can be changed by applying one or more of the "options" parameters. The option(s) must be contained within "a pair of quotes"
Within a FOR loop the visibility of FOR variables is controlled via SETLOCAL EnableDelayedExpansion
tokens=2,4,6 will cause the second, fourth and sixth items on each line to be processed
tokens=2-6 will cause the second, third, fourth, fifth and sixth items on each line to be processed
tokens=* will cause all items on each line to be processed
tokens=3* will cause the 3rd and all subsequent items on each line to be processed
Each token specified will cause a corresponding parameter letter to be allocated.
If the last character in the tokens= string is an asterisk, then additional parameters are allocated for all the remaining text on the line.
More than one delimiter may be specified so a string like 'abcd+efg+hijk+lmno;pqr;stu+vwzyz' can be broken up using "delims=;+".
You can use any character as a delimiter, but they are case sensitive.
If you don't specify delims it will default to "delims=<tab><space>"
n.b. some text editors will enter the TAB character as a series of spaces, specifying more than one delimiter has been known to cause problems with some data sets.
This option is useful when dealing with a filenameset that is a long filename containing spaces, it allows you to put double quotes around the filename.
The backquote character ` is just below the ESC key on most keyboards.
The default end-of-line character is a semicolon ';' when the FOR command reads a text file (or even a character string), any line that STARTS with the eol character will be ignored. In other words it is treated as a comment.
Use eol=X to change the eol character to X.
Most often you will want to turn this feature off so that every line of your data file is processed, in theory "eol=" should turn this feature off, but in practice this fails to work correctly so instead set eol to some unusual character that you don't expect to ever be in the data file e.g. "eol=€" or "eol=¬".
Extracting data from this text file:
FOR /F "tokens=1,3 delims=," %%G IN (weather.txt) DO @echo %%G %%H
The tricky part is splitting up each the line into the right tokens, in this case I'm splitting on the comma character ',' this splits the line into 3 chunks of text and we pull out the first and third items with "tokens=1,3"
%%G is declared in the FOR statement and %%H is implicitly declared via the tokens= option. You can specify up to 26 tokens via the tokens= line, provided this does not cause an attempt to declare a parameter higher than the letter 'Z'.
FOR parameter names are global, so in complex scripts which call one FOR statement from within another FOR statement you can refer to both sets of parameters. You cannot have more than 26 parameters active at any one time.
Parse a text string:
A string of text will be treated just like a single line of input from a file, the string must be enclosed in double quotes (or single quotes with usebackq).
Echo just the date from the following string
FOR /F "tokens=4 delims=," %%G IN ("deposit,$4500,123.4,12-AUG-09") DO @echo Date paid %%G
Parse the output of a command:
FOR /F %%G IN ('"C:\program Files\command.exe"') DO ECHO %%G
Parse the contents of a file:
FOR /F "tokens=1,2* delims=," %%G IN (C:\MyDocu~1\mytex~1.txt) DO ECHO %%G
FOR /F "usebackq tokens=1,2* delims=," %%G IN ("C:\My Documents\my textfile.txt") DO ECHO %%G
To specify an exact set of files to be processed, such as all .MP3 files in a folder including subfolders and sorted by date - just use the DIR /b command to create the list of filenames ~ and use this variant of the FOR command syntax.
Many of the newer commands and utilities (e.g. WMIC) output text files in unicode format, these cannot be read by the FOR command which expects ASCII.
To convert the file format use the TYPE command.
"It's completely intuitive; it just takes a few days to learn, but then it's completely intuitive" - Terry Pratchett.
FOR - Loop commands
FOR - Loop through a set of files in one folder
FOR /R - Loop through files (recurse subfolders)
FOR /D - Loop through several folders
FOR /L - Loop through a range of numbers
FOR /F - Loop through the output of a command
FORFILES - Batch process multiple files
IF - Conditionally perform a command
SETLOCAL - Control the visibility of environment variables inside a loop
Powershell: ForEach-Object - Loop for each object in the pipeline