— as an argument on its own is standardized across all UNIX commands: It means that further arguments should be treated as positional arguments, not options. See Guideline 10 in POSIX Utility Syntax Conventions. To give you a non-NPM-based example, ls — -l will look for a file named -l, because the — specified that … Read more
Unfortunately, bc doesn’t support scientific notation. However, it can be translated into a format that bc can handle, using extended regex as per POSIX in sed: sed -E ‘s/([+-]?[0-9.]+)[eE]\+?(-?)([0-9]+)/(\1*10^\2\3)/g’ <<<“$value” you can replace the “e” (or “e+”, if the exponent is positive) with “*10^”, which bc will promptly understand. This works even if the exponent … Read more
You will need to double-escape the $ character within the shell command: HEADER = $(shell for file in `find . -name *.h`;do echo $$file; done) The problem here is that make will try to expand $f as a variable, and since it doesn’t find anything, it simply replaces it with “”. That leaves your shell … Read more
Here is one method: $ awk ‘{s+=$1}END{print “ave:”,s/NR}’ RS=” ” file ave: 54.646
That particular feature is called quick substitution; its documentation can be found in the Event Designators section of the Bash Manual. You can’t do what you want with quick substitution; you’ll have to resort to something slightly more verbose: !!:gs/foo/bar/
It’s not pure bash, but much easier with the Perl version of rename: rename ‘s/\d+/sprintf(“%05d”,$&)/e’ foo* Where ‘s/\d+/sprintf(“%05d”,$&)/e’ is the Perl replace regular expression. \d+ will match the first set of numbers (at least one number) sprintf(“%05d”,$&) will pass the matched numbers to Perl’s sprintf, and %05d will pad to five digits
With all due respect to the users of pgrep, pkill, ps | awk, etc, there is a much better way. Consider that if you rely on ps -aux | grep … to find a process you run the risk of a collision. You may have a use case where that is unlikely, but as a … Read more
The following should do it: (command1; command2) Note the added parentheses.
Rule of thumb: Use -a and -o inside square brackets, && and || outside. It’s important to understand the difference between shell syntax and the syntax of the [ command. && and || are shell operators. They are used to combine the results of two commands. Because they are shell syntax, they have special syntactical … Read more