read from file
Type
command
Summary
Takes data from a file that has been opened with the open file command, and places the data in the it variable.
Syntax
read from {file <pathName> | stdin} [at <start>] {until {<string> | end | EOF | empty} | for <amount> [<chunkType>]} [in <time>]
Description
Use the read from file command to get data from a file.
The pathName is case-sensitive, even on platforms where file names are not case-sensitive. It must be exactly the same--including the case of characters--as the name you used with the open file command.
If you specify the name of a serial port on Mac OS or Windows systems, LiveCode reads from the specified port. The names of serial ports end in a colon (:).
The start specifies the character or byte position in the file where you want to begin reading. A positive number begins start characters after the beginning of the file; a negative number begins start characters before the end of the file.
The string is any expression that evaluates to a string. When LiveCode encounters the string in the file, it stops reading. If the string is not encountered, the read from file command continues reading until it reaches the end of the file.
If you specify any of EOF, end, or empty, the read continues reading until it reaches the end of the file. (If you're reading from a serial port, you must use the form read from file portname until empty.)
The amount is a positive integer and specifies how much data to read.
The chunkType is one of chars, characters, words, items, lines, int1, uInt1, int2, uint2, int4, or uint4. The read from file command reads amount of the specified chunkType. If you don't specify a chunkType, amount characters are read from the file.
The time is the time to wait for the read to be completed, in milliseconds, seconds, or ticks.
If you don't specify a start, LiveCode begins at the position determined by the seek command, or wherever the last read from file or write to file command to that file left off, or at the first character, if the file has not been accessed since being opened, or at the last character, if the file was opened in append mode.
The until string form reads data until the specified string is encountered. The until end, until EOF, and until empty forms are synonyms, and read data up to the end of the file. You can read an entire file by opening it and reading until the end:
open file fileToRead
read from file fileToRead until EOF
close file fileToRead
The read from stdin form reads from the standard input (on Unix systems). The standard input is always open, so you can read from it without first opening it.
As an alternative to the open file and read from file commands, you can also use the URL keyword with get and other commands to access the contents of a file.
Parameters
| Name | Type | Description |
|---|---|---|
pathName | The pathName specifies the name and location of the file you want to read from. It must be the same as the path you used with the open file command.
| |
start | The start specifies the character or byte position in the file where you want to begin reading. A positive number begins start characters after the beginning of the file; a negative number begins start characters before the end of the file. | |
string | string | When LiveCode encounters the string in the file, it stops reading. If the string is not encountered, the read from file command continues reading until it reaches the end of the file. |
amount | A positive integer and specifies how much data to read. | |
chunkType | One of chars, characters, words, items, lines, int1, uInt1, int2, uint2, int4, or uint4. The read from file command reads amount of the specified chunkType. If you don't specify a chunkType, amount characters are read from the file. | |
time | The time to wait for the read to be completed, in milliseconds, seconds, or ticks. |
Examples
read from file "Test" for 8 -- reads 8 characters
read from file "COM1:" at 20 until EOF
read from file (field "Datafile") at -100 for charsToRead
read from stdin for 1 line
Related
glossary: platform, binary file, variable, byte, case-sensitive, keyword, negative, expression, command, evaluate
keyword: file, characters, string, character, integer, it, URL
command: write to file, close file, open file, seek, get
constant: CRLF
control structure: function
function: ticks, result, milliseconds
Compatibility and Support
Introduced
LiveCode 1.0
OS
mac
windows
linux
ios
android
Platforms
desktop
server
mobile