ruby檔案讀寫的好文章 ruby way之IO之一
http://simohayha.javaeye.com/blog/153398
1 開啟和關閉一個檔案類方法File.new 開啟一個檔案，並將它例項化為一個File物件，他的第一個引數是檔名.
可選的第二個引數叫做 mode string(這個也是從c得來的).他的意思是怎樣開啟一個檔案(讀，寫或者其他的).預設是'r'(也就是讀).
Ruby程式碼
- file1 = File.new("one") # Open for reading
- file2 = File.new("two","w") # Open for writing
另外一種new的形式是三個引數的,其中第二個引數是指定了這個檔案的原始的許可權(經常表示為一個八進位制的數).第三個引數是一系列Ored標誌 的組合.標誌是個常量比如File:CREAT(如果檔案不存在則建立它)和File:RDONLY(以只讀方式開啟檔案)。不過這種形式很少使用：file1 = File.new("one") # Open for reading file2 = File.new("two", "w") # Open for writing
Ruby程式碼
- file = File.new("three", 0755,File::CREAT|File::WRONLY)
file = File.new("three", 0755, File::CREAT|File::WRONLY)出於對作業系統和執行環境的考慮，如果你打開了一個檔案的話，你就必須關閉它。當你開啟一個檔案用於寫時，你更應該這樣做，從而才能免於丟失資料.close方法就是關閉一個檔案：
Ruby程式碼
- out = File.new("captains.log","w")
- # Process as needed...
- out.close
out = File.new("captains.log", "w") # Process as needed... out.close這裡還有一個open方法，它的最簡單的形式是和new同義的：
Ruby程式碼
- trans = File.open("transactions","w")
trans = File.open("transactions","w")但是open方法還能夠帶一個block作為引數，當存在block時，開啟的檔案將會做為一個引數傳遞給block.這時這個檔案將會在這個block的作用域裡，保持開啟，直到block結束時，自動關閉:
Ruby程式碼
- File.open("somefile","w")do |file|
- file.puts "Line 1"
- file.puts "Line 2"
- file.puts "Third and final line"
- end
File.open("somefile","w") do |file| file.puts "Line 1" file.puts "Line 2" file.puts "Third and final line" end2 更新檔案
假設我們想要開啟一個檔案用於讀和寫，簡單的加一個'+'號到file mode就行了:
Ruby程式碼
- f1 = File.new("file1","r+")
- # Read/write, starting at beginning of file.
- f2 = File.new("file2","w+")
- # Read/write; truncate existing file or create a new one.
- f3 = File.new("file3","a+")
- # Read/write; start at end of existing file or create a
- # new one.
f1 = File.new("file1", "r+") # Read/write, starting at beginning of file. f2 = File.new("file2", "w+") # Read/write; truncate existing file or create a new one. f3 = File.new("file3", "a+") # Read/write; start at end of existing file or create a # new one.3 追加一個檔案
假設我們想要追加一段資訊到一個存在檔案，當我們開啟檔案時使用'a'作為file mode就行了:
Ruby程式碼
- logfile = File.open("captains_log","a")
- # Add a line at the end, then close.
- logfile.puts "Stardate 47824.1: Our show has been canceled."
- logfile.close
logfile = File.open("captains_log", "a") # Add a line at the end, then close. logfile.puts "Stardate 47824.1: Our show has been canceled." logfile.close4隨機存取一個檔案
如果你想隨即存取一個檔案，你能夠使用seek方法，它是File從Io繼承而來的.它的最簡單的使用就是指定一個位元組位置.這個位置是相對於檔案開始的位置(開始的位置是0):
Ruby程式碼
- # myfile contains only: abcdefghi
- file = File.new("myfile")
- file.seek(5)
- str = file.gets # "fghi"
# myfile contains only: abcdefghi file = File.new("myfile") file.seek(5) str = file.gets # "fghi"如果你能確定每一行都是固定的長度，你就能seek指定的行：
Ruby程式碼
- # Assume 20 bytes per line.
- # Line N starts at byte (N-1)*20
- file = File.new("fixedlines")
- file.seek(5*20) # Sixth line!
- # Elegance is left as an exercise.
# Assume 20 bytes per line. # Line N starts at byte (N-1)*20 file = File.new("fixedlines") file.seek(5*20) # Sixth line! # Elegance is left as an exercise.Ruby程式碼
- file = File.new("somefile")
- file.seek(55) # Position is 55
- file.seek(-22, IO::SEEK_CUR) # Position is 33
- file.seek(47, IO::SEEK_CUR) # Position is 80
file = File.new("somefile") file.seek(55) # Position is 55 file.seek(-22, IO::SEEK_CUR) # Position is 33 file.seek(47, IO::SEEK_CUR) # Position is 80你也能從檔案的結束位置開始搜尋:
Ruby程式碼
- file.seek(-20, IO::SEEK_END) # twenty bytes from eof
file.seek(-20, IO::SEEK_END) # twenty bytes from eofRuby程式碼
- file.seek(20)
- pos1 = file.tell # 20
- file.seek(50, IO::SEEK_CUR)
- pos2 = file.pos # 70
file.seek(20) pos1 = file.tell # 20 file.seek(50, IO::SEEK_CUR) pos2 = file.pos # 705 操作二進位制檔案
在很久以前，c語言通過在file mode後附加一個'b'來表示將檔案用二進位制模式開啟.在今天，二進位制檔案的處理已經沒有那麼麻煩了。在ruby中，一個字串很容易儲存一個二進位制資料，而且也不用通過任何特殊的方式來讀檔案.
可是在windows下是例外，在他下面，二進位制檔案和文字檔案的不同是，在二進位制mode下，結束行不能被轉義為一個單獨的換行，而是被儲存為一個回車換行對.
另外的不同是，在文字模式下 control-Z被作為檔案的結束:
Ruby程式碼
- # Create a file (in binary mode)
- File.open("myfile","wb") {|f| f.syswrite("12345\0326789\r") }
- # Above note the embedded octal 032 (^Z)
- # Read it as binary
- str = nil
- File.open("myfile","rb") {|f| str = f.sysread(15) }
- puts str.size # 11
- # Read it as text
- str = nil
- File.open("myfile","r") {|f| str = f.sysread(15) }
- puts str.size # 5
# Create a file (in binary mode) File.open("myfile","wb") {|f| f.syswrite("12345\0326789\r") } # Above note the embedded octal 032 (^Z) # Read it as binary str = nil File.open("myfile","rb") {|f| str = f.sysread(15) } puts str.size # 11 # Read it as text str = nil File.open("myfile","r") {|f| str = f.sysread(15) } puts str.size # 5再看下面的程式碼：
Ruby程式碼
- # Input file contains a single line: Line 1.
- file = File.open("data")
- line = file.readline # "Line 1.\n"
- puts "#{line.size} characters." # 8 characters
- file.close
- file = File.open("data","rb")
- line = file.readline # "Line 1.\r\n"
- puts "#{line.size} characters." # 9 characters 二進位制模式的結尾是一個回車換行對.
- file.close
# Input file contains a single line: Line 1. file = File.open("data") line = file.readline # "Line 1.\n" puts "#{line.size} characters." # 8 characters file.close file = File.open("data","rb") line = file.readline # "Line 1.\r\n" puts "#{line.size} characters." # 9 characters 二進位制模式的結尾是一個回車換行對. file.closeRuby程式碼
- file = File.open("data")
- file.binmode
- line = file.readline # "Line 1.\r\n"
- puts "#{line.size} characters." # 9 characters
- file.close
file = File.open("data") file.binmode line = file.readline # "Line 1.\r\n" puts "#{line.size} characters." # 9 characters file.closeRuby程式碼
- input = File.new("myfile",'a+')
- output = File.new("outfile",'a+')
- instr = input.sysread(10);
- puts instr
- bytes = output.syswrite("This is a test.")
input = File.new("myfile",'a+') output = File.new("outfile",'a+') instr = input.sysread(10); puts instr bytes = output.syswrite("This is a test.")如果檔案指標已經到達檔案的結尾時，sysread方法將會丟擲一個異常.
這邊要注意 Array 的pack和string的unpack方法，對於處理二進位制資料非常有用.
=======================================================
讀檔案:
第一種方法:
$result='d:\\rs.txt'
File.open($result, "r") do |file|
file.each_line do |line|
if line.length>20
puts line.chop.length #去掉最後一個換行字元,並顯示該行實際字串的長度
puts line
end
end
end
第二種方法:
filename='d:\\rs.txt'
while File.exists?(filename) #如果原始檔存在就執行下面的操作
file=File.open(filename,'r')
while (lines=file.gets)
puts lines
end
寫檔案:
$filename="C:\\Automation\\rss"+".txt"
$logfile = File.new($filename,"a")
iCount=0
while(iCount<10) //迴圈寫入10行
$logfile.puts "http://xxxx/rs#{iCount}.xml"
iCount=iCount+1
end
今天又笨了一次,由於要比較兩個檔案的不同,於是考慮用ruby來寫個指令碼
實現,剛開始的時候使用雙重
File.open($file1, "r") do |file1|
file1.each_line do |line1|
總是報錯,
後來改成先把檔案讀到一個數組裡,然後迴圈比較,成功.
其實這是個笨方法,在unix下使用三個命令就可以完成了.
1.先使用sort指令將檔案中的資料按照要求的索引進行排序,
2.然後使用uniq指令將重複資料去掉
3.再使用diff命令就可以了.
========================================
ruby讀寫文字檔案的簡單例子，除了演示文字檔案的讀寫外，這段ruby程式可以從文字檔案中刪除包含某些字串的行。
用法：ruby delline.rb 檔名 字串1 字串2 字串n
將刪除同時包含字串1 字串2 字串n的行。
ruby的開發環境這裡下載
http://www.ruby-lang.org/en/downloads/
直接下載最近的穩定版Windows安裝包
http://rubyforge.org/frs/download.php/29263/ruby186-26.exe
程式碼如下
- ifARGV.length<2then
- puts"USAGE: ruby delline.rb text_file_name str1 [str2 ...]"
- exit
- end
- i_file_name = ARGV[0]
- i_file_name_bak = i_file_name +".bak"
- ifFileTest.exist?(i_file_name)then
- File.rename(i_file_name,i_file_name_bak)
- else
- puts"File #{i_file_name} was not found"
- exit
- end
- i_file = File.new(i_file_name_bak,"r")
- o_file = File.new(i_file_name,"w")
- i_file.each_linedo |line|
- delete_flag =true
- 1.upto(ARGV.length - 1)do |x|
- if !line.include?(ARGV[x])then
- delete_flag =false
- break
- end
- end
- o_file.putslineif !delete_flag
- end
- i_file.close
- o_file.close
File.open("cmd.txt","r") do |file|
while line=file.gets
puts line
end
end
puts
file=File.new("cmd.txt","r")
file.each_line do |line|
puts line
end
IO.foreach("cmd.txt") do |line|
puts line if line =~ /target/
puts line if line !~ /target/
end
# Another way...
file = File.new("cmd.txt")
file.each do |line|
puts line if line =~ /target/
end
arr = IO.read("cmd.txt")
bytes = arr.size
puts "myfile has #{bytes} bytes in it."
arr = IO.readlines("cmd.txt")
puts arr
lines = arr.size
puts "myfile has #{lines} lines in it."
file2=File.new("cmd.txt");
puts File.expand_path("cmd.txt")
file = File.new("cmd.txt")
e_count = 0
file.each_byte do |byte|
e_count += 1 if byte == ?e
end
puts File.exist?("testR.txt")
file1=File.new("testR.txt","w") #沒有檔案則會自動建立
puts File.exist?("testR.txt")
puts file1.write("ttt333\nttt444\n")
字串當檔案用.rb
require 'stringio'
ios = StringIO.new("abcdefghijkl\nABC\n123")
ios.seek(5)
ios.puts("xyz")
puts ios.tell # 8
puts ios.string.dump # "abcdexyzijkl\nABC\n123"
c = ios.getc
puts "c = #{c}" # c = 105
ios.ungetc(?w)
puts ios.string.dump # "abcdexyzwjkl\nABC\n123"
puts "Ptr = #{ios.tell}"
s1 = ios.gets # "wjkl"
s2 = ios.gets # "ABC"