\nIt’s Day Two of Batch File Week.\nDon’t worry, it’ll be over in a few days.\n<\/p>\n
\nThere is no obvious way to read the output of a command\ninto a batch file variable.\nIn unix-style shells, this is done via backquoting.\n<\/p>\n
\nx=`somecommand`\n<\/pre>\n\nThe Windows command processor does not have direct backquoting,\nbut you can fake it by abusing the
FOR<\/code> command.\nHere’s the evolution:\n<\/p>\n\nThe
\/F<\/code> flag to theFOR<\/code> command says\nthat it should open the file you pass in parentheses and set\nthe loop variable to the contents of each line.\n<\/p>\n\nfor \/f %%i in (words.txt) do echo [%%i]\n<\/pre>\n\nThe loop variable in the
FOR<\/code> command takes one\npercent sign if you are executing it directly from the command prompt,\nbut two percent signs if you are executing it from a batch file.\nI’m going to assume you’re writing a batch file, so if you want\nto practice from the command line, remember to collapse the double\npercent signs to singles.\n<\/p>\n\nI’m cheating here because I know that
words.txt<\/code>\ncontains one word per line.\nBy default,\ntheFOR<\/code> command sets the loop variable to the first\nword of each line.\nIf you want to capture the entire line, you need to change the delimiter.\n<\/p>\n\nfor \/f \"delims=\" %%i in (names.txt) do echo [%%i]\n<\/pre>\n\nThere are other options for capturing say the first and third word\nor whatever.\nSee the
FOR \/?<\/code> online help for details.\n<\/p>\n\nNow, parsing files is not what we want, but it’s closer.\nYou can put the file name in single quotes\nto say “Instead of opening this file and reading the contents,\nI want you to run this command<\/i> and read the contents.”\nFor example, suppose you have a program called\n
printappdir<\/code> which outputs a directory,\nand you want a batch file that changes to that directory.\n<\/p>\n\nfor \/f \"delims=\" %%i in ('printappdir') do cd \"%%i\"\n<\/pre>\n\nWe ask the
FOR<\/code> command to run theprintappdir<\/code>\nprogram and execute the commandcd \"%%i\"<\/code> for each\nline of output.\nSince the program has only one line of output,\nthe loop executes only once, and the result is that the directory\nis changed to the path that the\nprintappdir<\/code> program prints.\n<\/p>\n\nIf you want to capture the output into a variable,\njust update the action:\n<\/p>\n
\nfor \/f %%i in ('printappdir') do set RESULT=%%i\necho The directory is %RESULT%\n<\/pre>\n\nIf the command has multiple lines of output, then this will\nend up saving only the last line, since previous lines get\noverwritten by subsequent iterations.\n<\/p>\n
\nBut what if the line you want to save isn’t the last line?\nOr what if you don’t want the entire line?\n<\/p>\n