You can achieve something similar by abusing the –rcfile option: bash –rcfile <(echo “export PS1=’> ‘ && ls”) From bash manpage: –rcfile file Execute commands from file instead of the system wide initialization file /etc/bash.bashrc and the standard personal initialization file ~/.bashrc if the shell is interactive
Here’s how to compare versions. using sort -V: function version_gt() { test “$(printf ‘%s\n’ “$@” | sort -V | head -n 1)” != “$1”; } example usage: first_version=5.100.2 second_version=5.1.2 if version_gt $first_version $second_version; then echo “$first_version is greater than $second_version !” fi pro: solid way to compare fancy version strings: support any length of sub-parts … Read more
In sed, assuming the strings don’t contain any newline characters: string1=”test toast” string2=”test test” printf “%s\n%s\n” “$string1” “$string2” | sed -e ‘N;s/^\(.*\).*\n\1.*$/\1/’
Citing this source, Standard UNIX variables are split into two categories, environment variables and shell variables. In broad terms, shell variables apply only to the current instance of the shell and are used to set short-term working conditions; environment variables have a farther reaching significance, and those set at login are valid for the duration … Read more
You’re printing the result of the gsub, but gsub does an in-place modify of $2 instead of returning a modified copy. Call gsub, then print: awk -F\, ‘{gsub(/[ \t]+$/, “”, $2); print $2 “:”}’
The parent shell, the one invoking bash show_files.sh *, expands the * for you. In your script, you need to use: for dir in “$@” do echo “$dir” done The double quotes ensure that multiple spaces etc in file names are handled correctly. See also How to iterate over arguments in a bash shell script. … Read more
Another very handy way to do this is with gnu parallel, which is well worth installing if you don’t already have it; this is invaluable if the tasks don’t necessarily take the same amount of time. seq 1000 | parallel -j 8 –workdir $PWD ./myrun {} will launch ./myrun 1, ./myrun 2, etc, making sure … Read more
You can either use: “texta’textb” (APOSTROPHE inside QUOTATION MARKs) or ‘texta’\”textb’ (APOSTROPHE text APOSTROPHE, then REVERSE SOLIDUS, APOSTROPHE, then APOSTROPHE more text APOSTROPHE) I used unicode character names. REVERSE SOLIDUS is more commonly known as backslash. In the latter case, you close your apostrophe, then shell-quote your apostrophe with a backslash, then open another apostrophe … Read more
— as an argument on its own is standardized across all UNIX commands: It means that further arguments should be treated as positional arguments, not options. See Guideline 10 in POSIX Utility Syntax Conventions. To give you a non-NPM-based example, ls — -l will look for a file named -l, because the — specified that … Read more
Unfortunately, bc doesn’t support scientific notation. However, it can be translated into a format that bc can handle, using extended regex as per POSIX in sed: sed -E ‘s/([+-]?[0-9.]+)[eE]\+?(-?)([0-9]+)/(\1*10^\2\3)/g’ <<<“$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