You can always check the man page of your shell. man bash says: Special Parameters # Expands to the number of positional parameters in decimal. Therefore a shell script can check how many parameters are given with code like this: if [ "$#" -eq 0 ]; then echo "you did not pass any parameter" fi

In shell terminology, eval is a built-in, not a function. In practice, built-ins behave a lot like functions that don't have an in-language definition, but not quite (as becomes apparent if you are twisted enough to define a function called eval ).

2015年6月19日 · Interestingly, the shell will even do the twiddle thing ~ and << left and >> right SHIFTs. And so if a is true OR b^100 is true, the expansion evals to 1, matches the comparison -eq [test ] and the shell continues to evaluate the rest of && some commands. It is usually easier to evaluate/compare integers in that way than to try to string ...

Kernel Version. If you want kernel version information, use uname(1). For example: $ uname -a Linux localhost 3.11.0-3-generic #8-Ubuntu SMP Fri Aug 23 16:49:15 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

2014年3月19日 · Stack Exchange Network. Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

You can find a very nice reference for bash's [aka test builtin's operators here, or by running help test in a bash shell or info bash test or info bash '[' from any shell¹. If you are using a different shell, just search for the description of its [ or test builtin in its documentation of if it doesn't have such a builtin², in the man page ...

A shell assignment is a single word, with no space after the equal sign. So what you wrote assigns an empty value to thefile; furthermore, since the assignment is grouped with a command, it makes thefile an environment variable and the assignment is local to that particular command, i.e. only the call to ls sees the assigned value.

2013年6月14日 · Using POSIX shell functions, and awk math power, just define this (one line) function: calc(){ awk "BEGIN { print $*}"; } Then just execute things like calc 1+1 or calc 5/2. Note: To make the function always available, add it to ~/.bashrc (or your corresponding shell's startup file) Of course, a little script named "calc" with the following ...

2017年6月13日 · Possible duplicate of Shell test to find a pattern in a string – user34720. Commented Mar 27, 2019 at 13:05.

After googling a bit I couldn't find a simple way to use a shell command to generate a random decimal integer number included in a specific range, that is between a minimum and a maximum. I read a...