There are two typical ways of declaring a function. I prefer the second approach. function function_name { command… } or function_name () { command… } To call a function with arguments: function_name “$arg1” “$arg2” The function refers to passed arguments by their position (not by name), that is $1, $2, and so forth. $0 is … Read more
Revised Answer (Feb 12, 2014) the_world_is_flat=true # …do something interesting… if [ “$the_world_is_flat” = true ] ; then echo ‘Be careful not to fall off!’ fi Original Answer Caveats: https://stackoverflow.com/a/21210966/89391 the_world_is_flat=true # …do something interesting… if $the_world_is_flat ; then echo ‘Be careful not to fall off!’ fi From: Using boolean variables in Bash The reason … Read more
Use wc: wc -l <filename> This will output the number of lines in <filename>: $ wc -l /dir/file.txt 3272485 /dir/file.txt Or, to omit the <filename> from the result use wc -l < <filename>: $ wc -l < /dir/file.txt 3272485 You can also pipe data to wc as well: $ cat /dir/file.txt | wc -l 3272485 … Read more
In bash (>=4.2) it is preferable to use printf’s built-in date formatter (part of bash) rather than the external date (usually GNU date). As such: # put current date as yyyy-mm-dd in $date # -1 -> explicit current date, bash >=4.3 defaults to current time if not provided # -2 -> start time for shell … Read more
The command you want is named tee: foo | tee output.file For example, if you only care about stdout: ls -a | tee output.file If you want to include stderr, do: program [arguments…] 2>&1 | tee outfile 2>&1 redirects channel 2 (stderr/standard error) into channel 1 (stdout/standard output), such that both is written as stdout. … Read more
You should use #!/usr/bin/env bash for portability: different *nixes put bash in different places, and using /usr/bin/env is a workaround to run the first bash found on the PATH. And sh is not bash.
You could do this, which facilitates reading: >&2 echo “error” >&2 copies file descriptor #2 to file descriptor #1. Therefore, after this redirection is performed, both file descriptors will refer to the same file: the one file descriptor #2 was originally referring to. For more information see the Bash Hackers Illustrated Redirection Tutorial.
None of these solutions worked for me. Instead, I elaborate on @Martin v. Löwis ‘s mention of setting a config file for SSH. SSH will look for the user’s ~/.ssh/config file. I have mine setup as: Host gitserv Hostname remote.server.com IdentityFile ~/.ssh/id_rsa.github IdentitiesOnly yes # see NOTES below And I add a remote git repository: … Read more
The are various ways: POSIX standard tr $ echo “$a” | tr ‘[:upper:]’ ‘[:lower:]’ hi all AWK $ echo “$a” | awk ‘{print tolower($0)}’ hi all Non-POSIX You may run into portability issues with the following examples: Bash 4.0 $ echo “${a,,}” hi all sed $ echo “$a” | sed -e ‘s/\(.*\)/\L\1/’ hi all # … Read more
Bash alias does not directly accept parameters. You will have to create a function. alias does not accept parameters but a function can be called just like an alias. For example: myfunction() { #do things with parameters like $1 such as mv “$1” “$1.bak” cp “$2” “$1” } myfunction old.conf new.conf #calls `myfunction` By the … Read more