Read from a channel 

Tclsh Built-In Commands


read ?-nonewline? channelId

read channelId numChars


In the first form, the read command reads all of the data from channelId up to the end of the file. If the -nonewline switch is specified then the last character of the file is discarded if it is a newline. In the second form, the extra argument specifies how many characters to read. Exactly that many characters will be read and returned, unless there are fewer than numChars left in the file; in this case all the remaining characters are returned. If the channel is configured to use a multi-byte encoding, then the number of characters read may not be the same as the number of bytes read.

If channelId is in nonblocking mode, the command may not read as many characters as requested: once all available input has been read, the command will return the data that is available rather than blocking for more input. If the channel is configured to use a multi-byte encoding, then there may actually be some bytes remaining in the internal buffers that do not form a complete character. These bytes will not be returned until a complete character is available or end-of-file is reached. The -nonewline switch is ignored if the command returns before reaching the end of the file.

read translates end-of-line sequences in the input into newline characters according to the -translation option for the channel. See the fconfigure reference page for a discussion on ways in which fconfigure will alter input.


Windows 8.1. Windows Server 2012 R2. Windows 10. Windows Server 2016. Windows Server 2019. Windows 11. Windows Server 2022.


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eof, fblocked, fconfigure

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