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parallel:tldr:86451
This command is a combination of multiple commands and uses the cat and parallel utilities.
Explanation:
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cat: "cat" is a command used to concatenate and display the contents of files.
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${big_file-txt}: Here, ${big_file-txt} is a variable that should be replaced with the actual name of a big file (e.g., big_file.txt). This variable represents the input file whose contents will be processed.
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|: The vertical bar (|) is called a pipe. It is used to connect the output of one command to the input of another command.
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parallel: "parallel" is a command-line tool that allows executing multiple commands in parallel.
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--pipe: This option tells parallel to read the input from the pipe instead of command-line arguments.
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--block 1M: Here, --block 1M is an option of parallel that specifies the size of the block to be read from the input. In this case, it is 1MB (1 megabyte).
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${command}: Similar to ${big_file-txt}, this is another variable that should be replaced with the actual command you want to run on each block read from the input file.
To summarize, the command takes the content of the big_file.txt file, passes it through the pipe using cat, then parallel reads this input in blocks of 1 megabyte (--block 1M) and runs the specified command (${command}) on each block in parallel.