What does -f mean in an if statement in a bash script?
Jul 4, 2018 · fi. The command, in your case, is [ which is also known as test command. So it'd be perfectly valid to do. if test -f /etc/bashrc; then. . /etc/bashrc. fi. The -f flag verifies two things: the provided path exists and is a regular file. If /etc/bashrc is in fact a directory or missing, test should return non-zero exit status to signal failure.
Difference between $ {} and $ () in a shell script - Super User
76. $(command) is “command substitution”. As you seem to understand, it runs the command, captures its output, and inserts that into the command line that contains the $(…); e.g., ${parameter} is “parameter substitution”. A lot of information can be found in the shell’s man page, bash (1), under the “ Parameter Expansion ” heading:
What does $# mean in shell? - Unix & Linux Stack Exchange
the number of parameters with which the script has been called. the number of parameters which have been set within the script by set -- foo bar (when used within a function) the number of parameters with which a function has been called (set would work there, too). This is explained in the bash man page in the block "Special Parameters".
What is the meaning of $? in a shell script? - linux
Feb 20, 2011 · $0-The filename of the current script. $#-The number of arguments supplied to a script. $$-The process number of the current shell. For shell scripts, this is the process ID under which they are executing.
Shell scripting: -z and -n options with if - Unix & Linux Stack …
Jan 16, 2014 · To extend terdon's answer, I found that Unix / Linux - Shell Basic Operators on Tutorials Point also includes file-related operators (as well as other useful ones). -b file Checks if file is a block special file; if yes, then the condition becomes true.
scripting - How to use and/or conditional in shell script - Unix ...
Jun 19, 2015 · 1. Use arithmetic evaluation and parentheses to avoid ambiguity: Or, if you want to deal with strings as well, use [[. You want to omit those quoted (which don't make any sense anyway) if you want to be compatible with zsh. (( a != 0 || b != 100)) would do just the same as a ksh/zsh/bash only solution.
shell script - what is >> symbol and - Unix & Linux Stack Exchange
See What is the difference between > and >> (especially as it relates to use with the cat program)?, What does “3>&1 1>&2 2>&3” do in a script? and of course, your shell's manual. (There are some further explanations in Is this a typo in Bash manual's redirection section? too.) –
bash - Passing named arguments to shell scripts - Unix & Linux …
$ ./my_script -p '/some/path' -a5 Argument p_out is /some/path Argument arg_1 is 5 There is a helpful Small getopts tutorial or you can type help getopts at the shell prompt. Edit: The second case statement in while loop triggers if the -p option has no arguments and is followed by another option, e.g. my_script -p -a5, and exits the program.
shell - Starting with bash: -lt and -gt arguments - Unix & Linux …
Mar 19, 2014 · 11. You can find the definition of -lt and -gt in the documentation of the test command (man test), or in the documentation of bash since test is a built-in command in bash (like in most other shells). -lt and -gt are numeric comparisons (less-than [and not equal], greater-than [and not equal]). There are also less/greater-or-equal operators ...
How do I write a retry logic in script to keep retrying to run it upto ...
Dec 6, 2016 · I want to write logic in shell script which will retry it to run again after 15 sec upto 5 times based on "status code=FAIL" if it fails due to some issue.