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Linux Shell Tricks

Stdin as a file argument

# Command expects a file:
wc file1 file2
# Instead of making a temp file to read in a little text use this to pass in
# text as a temp file to STDIN
wc file1 - file2 # waits for you to type input and you complete this process by using `CTRL+D` which inserts the EOF character

Use the output of another command as a file argument

wc file1 <(echo “hello world”) file2

When you wrap a command with <(...) bash generate a temporal file in a path like /dev/fd/64, then execute your wrapped command, put the output in this temporal file, and finally replace <(...) with the filename of the temporal file, in this case, /dev/fd/64

Avoid conflicts with filenames that start with a dash

# -- indicates the end of the options section
# -myFile.txt uses a dash after the options section to avoid conflicts
cat -- -myFile.txt

Re-run commands

# of course there's
sudo !!
# but you can also do
!-N # where N is the Nth command (Relative)
# or
!N # for the N command in your history (Absolute)

Re-use command arguments

mkdir very-large-directory-name
cd very-large-directory-name
# Instead of duplicating the argument of the mkdir command, you can use !$ for retrieve the last argument of the last command, the result is:
mkdir very-large-directory-name
cd !$ # == cd very-large-directory-name

Ignore the first N lines

By default, the tail command will show the last n rows, but if you specified the option -n with a number that starts with the + symbol, like +5 , the first 5 lines are going to be skipped.

# In this example, the tail command is going to skip the first 10 lines and print the rest of the file content.
tail -n +10 dataset.csv

Track the content of a log file

See the contents of a file in real time

watch cat log.txt

Although this command does the job, it is not the best option. You can use the tail command with the -f option to track only the new lines that are appended to the file,

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