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Consider something like:
cat file | command > file Is this good practice? Could this overwrite the input file as the same time as we are reading it, or is it always read first in memory then piped to second command?
Obviously, I can use temp files as intermediary step, but I'm just wondering..
t=$(mktemp) cat file | command > ${t} && mv ${t} file 
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You cannot connect a pipe to a text file, or any other file, only to processes. Second, when using a pipe the process on the left side of the pipe is the one that uses STDOUT , and the process on the right side of the pipe uses STDIN .
"Tee" is explained in the Wikipedia article tee (command). Central is: "The tee command reads standard input, then writes its content to standard output and simultaneously copies it into the specified file(s) or variables.".
You can make it do so by using the pipe character '|'. Pipe is used to combine two or more commands, and in this, the output of one command acts as input to another command, and this command's output may act as input to the next command and so on.
To redirect the output of a command to a file, type the command, specify the > or the >> operator, and then provide the path to a file you want to the output redirected to. For example, the ls command lists the files and folders in the current directory.
No, it is not ok. All commands in a pipeline execute at the same time, and the shell prepares redirections before executing the commands. So, it is likely that the command will overwrite the file before cat reads it.
You need sponge(1) from moreutils.
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You can also use something like this (not recommended, use explicit temp files in production code):
{ rm file && your_command > file; } < file If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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