See the uuidgen program which is part of the e2fsprogs package. According to this, libuuid is now part of util-linux and the inclusion in e2fsprogs is being phased out. However, on new Ubuntu systems, uuidgen is now in the uuid-runtime package. To create a uuid and save it in a variable: uuid=$(uuidgen) On my Ubuntu … Read more
I don’t think a command or shell builtin for this exists, as it’s a trivial subset of what the Bourne shell for loop is designed for and implementing a command like this yourself is therefore quite simple. Per JimB’s suggestion, use the Bash builtin for generating sequences: for i in {1..10}; do command; done For … Read more
.bash_profile and .bashrc are specific to bash, whereas .profile is read by many shells in the absence of their own shell-specific config files. (.profile was used by the original Bourne shell.) .bash_profile or .profile is read by login shells, along with .bashrc; subshells read only .bashrc. (Between job control and modern windowing systems, .bashrc by … Read more
This: date +%s will return the number of seconds since the epoch. This: date +%s%N returns the seconds and current nanoseconds. So: date +%s%N | cut -b1-13 will give you the number of milliseconds since the epoch – current seconds plus the left three of the nanoseconds. and from MikeyB – echo $(($(date +%s%N)/1000000)) (dividing … Read more
There are several differences. In my opinion, a few of the most important are: [ is a builtin in Bash and many other modern shells. The builtin [ is similar to test with the additional requirement of a closing ]. The builtins [ and test imitate the functionality /bin/[ and /bin/test along with their limitations … Read more
This will return true if a variable is unset or set to the empty string (“”). if [ -z “${VAR}” ];
As of GNU coreutils 7.5 released in August 2009, sort allows a -h parameter, which allows numeric suffixes of the kind produced by du -h: du -hs * | sort -h If you are using a sort that does not support -h, you can install GNU Coreutils. E.g. on an older Mac OS X: brew … Read more
If you are on a OS X, this probably has nothing to do with the sed command. On the OSX version of sed, the -i option expects an extension argument so your command is actually parsed as the extension argument and the file path is interpreted as the command code. Try adding the -e argument explicitly and giving ” as argument to -i: See this.
For reading through a symlink1, which is usually not what you want (you usually don’t want to confuse the user this way), try: IMO, that’ll produce confusing output. “I ran foo.sh, but it’s saying I’m running bar.sh!? Must be a bug!” Besides, one of the purposes of having differently-named symlinks is to provide different functionality … Read more
Remove ; from the end of your script lines. This doesn’t happen in my bash, so I’m not sure what exactly is wrong, but my guess is this: ; is a separator of commands. Since your last command ends in ;, your bash probably expects another command after. Since the script finishes, though, it reads an empty command, which … Read more