This function opens a file using the specified file handle. The file handle may be an expression, the resulting value is used as the handle. If no filename is specified a variable with the same name as the file handle used (this should be a scalar variable with a string value referring to the file name). The special file name '-' refers to STDIN and '>-' refers to STDOUT.
以下是此函数的简单语法-
open FILEHANDLE, EXPR, LIST open FILEHANDLE, EXPR open FILEHANDLE
该函数在失败时返回o,在成功时返回1。
Following is the syntax to open file.txt in read-only mode. Here less than < sign indicates that file has to be opend in read-only mode.
open(DATA, "<file.txt");
DATA是将用于读取文件的文件句柄。这是打开文件并在屏幕上打印其内容的示例。
#!/usr/bin/perl open(DATA, "<file.txt"); while(<DATA>) { print "$_"; }
Following is the syntax to open file.txt in writing mode. Here less than > sign indicates that file has to be opend in writing mode −
open(DATA, ">file.txt");
This example actually truncates (empties) the file before opening it for writing, which may not be the desired effect. If you want to open a file for reading and writing, you can put a plus sign before the > or < characters.
例如,打开文件进行更新而不截断-
open(DATA, "+<file.txt");
首先截断文件-
open DATA, "+>file.txt" or die "Couldn't open file file.txt, $!";
您可以在追加模式下打开文件。在这种模式下,写入点将设置在文件末尾。
open(DATA,">>file.txt") || die "Couldn't open file file.txt, $!";
A double >> opens the file for appending, placing the file pointer at the end, so that you can immediately start appending information. However, you can.t read from it unless you also place a plus sign in front of it −
open(DATA,"+>>file.txt") || die "Couldn't open file file.txt, $!";
下表列出了不同模式的可能值。
Entities Definition < or r Read Only Access > or w Creates, Writes, and Truncates >> or a Writes, Appends, and Creates +< or r+ Reads and Writes +> or w+ Reads, Writes, Creates, and Truncates +>> or a+ Reads, Writes, Appends, and Creates
祝学习愉快!(内容编辑有误?请选中要编辑内容 -> 右键 -> 修改 -> 提交!)
Spring Cloud 微服务项目实战 -〔姚秋辰(姚半仙)〕