export makes the variable available to sub-processes. That is, export name=value means that the variable name is available to any process you run from that shell process. If you want a process to make use of this variable, use export, and run the process from that shell. name=value means the variable scope is restricted to … Read more
Simply type source ~/.bash_profile. Alternatively, if you like saving keystrokes, you can type . ~/.bash_profile.
set -x or set -o xtrace expands variables and prints a little + sign before the line. set -v or set -o verbose does not expand the variables before printing. Use set +x and set +v to turn off the above settings. On the first line of the script, one can put #!/bin/sh -x (or … Read more
There are a number of tools specifically designed for the purpose of manipulating JSON from the command line, and will be a lot easier and more reliable than doing it with Awk, such as jq: curl -s ‘https://api.github.com/users/lambda’ | jq -r ‘.name’ You can also do this with tools that are likely already installed on … Read more
*/ is a pattern that matches all of the subdirectories in the current directory (* would match all files and subdirectories; the / restricts it to directories). Similarly, to list all subdirectories under /home/alice/Documents, use ls -d /home/alice/Documents/*/
First redirect stderr to stdout — the pipe; then redirect stdout to /dev/null (without changing where stderr is going): command 2>&1 >/dev/null | grep ‘something’ For the details of I/O redirection in all its variety, see the chapter on Redirections in the Bash reference manual. Note that the sequence of I/O redirections is interpreted left-to-right, … Read more
There are a wealth of clipboards you could be dealing with. I expect you’re probably a Linux user who wants to put stuff in the X Windows primary clipboard. Usually, the clipboard you want to talk to has a utility that lets you talk to it. In the case of X, there’s xclip (and others). … Read more
To replace the first occurrence of a pattern with a given string, use ${parameter/pattern/string}: #!/bin/bash firstString=”I love Suzi and Marry” secondString=”Sara” echo “${firstString/Suzi/”$secondString”}” # prints ‘I love Sara and Marry’ To replace all occurrences, use ${parameter//pattern/string}: message=”The secret code is 12345″ echo “${message//[0-9]/X}” # prints ‘The secret code is XXXXX’ (This is documented in the … Read more
A simple answer is: echo ” lol ” | xargs Xargs will do the trimming for you. It’s one command/program, no parameters, returns the trimmed string, easy as that! Note: this doesn’t remove all internal spaces so “foo bar” stays the same; it does NOT become “foobar”. However, multiple spaces will be condensed to single … Read more
If you really want to use single quotes in the outermost layer, remember that you can glue both kinds of quotation. Example: alias rxvt=”urxvt -fg “”‘”‘#111111′”‘”‘ -bg ‘”‘”‘#111111′”‘” # ^^^^^ ^^^^^ ^^^^^ ^^^^ # 12345 12345 12345 1234 Explanation of how ‘”‘”‘ is interpreted as just ‘: ‘ End first quotation which uses single quotes. … Read more