Johnson峰的部落格

>>This page shows how to read specific lines from a text file. There are many ways to have the for /f command read the input file, for instance: 
這篇文章演示如何從檔中讀取特定的行.用for /f命令的多種變化方式可以達到該目的,例如： 
---------------------------------for /f----------------------------------------- 
for /f "delims=" %%a in (input.txt) do ... 
for /f "delims=" %%a in ('type input.txt') do ... 
for /f "delims=" %%a in ('more ^< input.txt') do ... 
---------------------------------for /f----------------------------------------- 

>>However, only the last method (using the more command) will give consistent results across Windows NT, 2000, XP and 2003. The first method does not recognise unicode files. Also, the usebackq switch must be used if the input filename contains spaces. The second method, using the type command, also fails to recognise unicode files on Windows 2000, XP and 2003 if the input file does not begin with a bit order mark (BOM). 
然而,只有最後一種方法(用到more命令的)在windows nt,2000,xp和2003中能夠得到一致的結果。第一種方法,不能有效的識別unicode編碼檔,同時,如果檔案名含有空格時,usebackq開關必須打開。第二種方法,用到type命令,同樣在windows nt,2000,xp和2003中,不能有效識別unicode編碼檔,同時,要求輸入的檔內容不能以位元序標誌(BOM)開頭. 

>>In all the examples, assume the contents of of the file numbers.txt to be: 
在如下所有的例子中,假設numbers.txt檔輸入以下內容： 
----------------------numbers.txt-------------------------- 
one 
two 
three 
four 
five 
six 
seven 
eight 
nine 
ten 
----------------------numbers.txt-------------------------- 

JT_man注：以下代碼中的setlocal ENABLEEXTENSIONS都可以刪除，因為系統預設命令處理器副檔名是啟動的。

>>Displaying the first line,This example prints one. 
顯示第一行,列印第一行的例子如下： 
------------------------1.bat------------------------------------------ 
@echo off & 

setlocal ENABLEEXTENSIONS 
set "first=" 
for /f "delims=" %%a in ('more ^< numbers.txt') do ( 
if not defined first set first=%%a 
) 
echo/%first% 
pause>nul 
------------------------1.bat-------------------------------------------

>>Displaying the first X lines,This example prints one, two and three. 
顯示前幾行,列印第一,二,三行的例子如下： 
------------------------123.bat------------------------------- 
@echo off & setlocal ENABLEEXTENSIONS 
set "lines=3" 
set i=-1 
set "ok=" 
for /f "delims=" %%a in ('more ^< numbers.txt') do ( 
      set/a i+=1 & for /f %%z in ('echo/%%i%%') do ( 
      if "%%z"=="%lines%" set ok=1 
      ) 
if not defined ok echo/%%a 
) 
pause>nul 
------------------------123.bat-------------------------------

JT_man注：或者

------------------------123_2.bat------------------------------- 

@echo off

setlocal enabledelayedexpansion

set "lines=3"

rem 顯示前3行

set i=-1  

set "ok="

for /f "delims=" %%a in ('more ^< numbers.txt') do (

      set /a i+=1

      if !i!==%lines% set ok=1

      if not defined ok echo %%a

) 

pause>nul 

------------------------123_2.bat------------------------------- 

>>Displaying the last line,This example prints ten. 
顯示最後一行,列印第十行的例子如下: 
------------------------10.bat-------------------------------------------- 
@echo off & setlocal ENABLEEXTENSIONS 
for /f "delims=" %%a in ('more ^< numbers.txt') do set "last=%%a" 
echo/%last% 
pause>nul 
------------------------10.bat-------------------------------------------- 

>>Displaying the last X lines,This example prints nine and ten. 
顯示最後x行,列印第9，10行的例子如下: 
------------------------lastx.bat----------------------------------------------- 
@echo off & setlocal ENABLEEXTENSIONS 
set "lines=2" 
for /f %%a in ('find/c /v "" ^< numbers.txt') do set/a skip=%%a-lines 
for /f "delims=" %%a in ('more/e +%skip% ^< numbers.txt') do ( 
:: 或者 for /f "skip=%skip% delims=" %%a in ('more ^< numbers.txt') do ( 
echo/%%a 
) 
pause>nul 
------------------------lastx.bat------------------------------------------------

>>Displaying the Nth line,This example prints three. 
Note that instead of using the more command's /e switch, the skip option could have been used with the for /f command, however, this fails is it is set to any number less than one. 
顯示第n行,列印第三行. 
注意啟用more命令的擴展功能(/e)開關,同時,ship選項過去常用於for /f命名中,但是當設定的數目小於實際值時,將導致失敗 
------------------------Nth.bat----------------------------------------------- 
@echo off & setlocal ENABLEEXTENSIONS
set LineNo=3
set "line="
set/a LineNo-=1
for /f "delims=" %%a in ('more/e +%LineNo% ^< numbers.txt') do (
if not defined line set "line=%%a"
)
echo/%line%
pause>nul
------------------------Nth.bat------------------------------------------------

>>Displaying the Nth line plus X number of lines,This example prints five and six. 
顯示第n+x行,列印第5,6行的例子如下: 
------------------------x+Nth.bat-------------------------------------------------- 
@echo off & setlocal ENABLEEXTENSIONS
set start=5
set "lines=2"
set/a i=-1,start-=1
set "ok=" 
for /f "delims=" %%a in ('more/e +%start% ^< numbers.txt') do (
set/a i+=1 & for /f %%z in ('echo/%%i%%') do (
if "%%z"=="%lines%" set ok=1
)
if not defined ok echo/%%a
)
pause>nul 
------------------------x+Nth.bat----------------------------------------------------

JT_man注：或者

------------------------通用.bat-------------------------------------------------- 

@echo off

setlocal enabledelayedexpansion

set start=5

rem 開始顯示的行號

set "lines=2"

rem 要顯示的行數

set/a i=-1,start-=1

set "ok=" 

for /f "skip=%start% delims=" %%a in ('more ^< numbers.txt') do (

      set/a i+=1

      if "!i!"=="%lines%" set ok=1

      if not defined ok echo/%%a

)

pause>nul 

------------------------通用.bat--------------------------------------------------