Run a string as a command within a Bash script
You can use eval to execute a string:
bash
How to modify a global variable within a function in bash?
When you use a command substitution (i.e., the $(…) construct), you are creating a subshell. Subshells inherit variables from their parent shells, but this only works one way: A subshell cannot modify the environment of its parent shell. Your variable e is set within a subshell, but not the parent shell. There are two ways to pass values from … Read more
-bash: export: `=’: not a valid identifier
You cannot put spaces around the = sign when you do: Remove the spaces you have and you should be good to go. If you type: the shell will interpret that as a request to export three names: foo, = and bar. = isn’t a valid variable name, so the command fails. The variable name, equals sign and it’s value must not be … Read more
How to modify a global variable within a function in bash?
When you use a command substitution (i.e., the $(…) construct), you are creating a subshell. Subshells inherit variables from their parent shells, but this only works one way: A subshell cannot modify the environment of its parent shell. Your variable e is set within a subshell, but not the parent shell. There are two ways to pass values from … Read more
Check number of arguments passed to a Bash script
Just like any other simple command, [ … ] or test requires spaces between its arguments. Or Suggestions When in Bash, prefer using [[ ]] instead as it doesn’t do word splitting and pathname expansion to its variables that quoting may not be necessary unless it’s part of an expression. It also has some other … Read more
Difference between return and exit in Bash functions
From man bash on return [n]; Causes a function to stop executing and return the value specified by n to its caller. If n is omitted, the return status is that of the last command executed in the function body. … on exit [n]: Cause the shell to exit with a status of n. If n is omitted, the … Read more
Binary Data Posting with curl
You don’t need –header “Content-Length: $LENGTH”. curl –request POST –data-binary “@template_entry.xml” $URL Note that GET request does not support content body widely. Also remember that POST request have 2 different coding schema. This is first form: $ nc -l -p 6666 & $ curl –request POST –data-binary “@README” http://localhost:6666 POST / HTTP/1.1 User-Agent: curl/7.21.0 (x86_64-pc-linux-gnu) libcurl/7.21.0 OpenSSL/0.9.8o … Read more
How do I edit $PATH (.bash_profile) on OS X?
You have to open that file with a text editor and then save it. It will open the file with TextEdit, paste your things and then save it. If you open it again you’ll find your edits. You can use other editors: But if you don’t know how to use them, it’s easier to use the open approach. … Read more
Is there a “goto” statement in bash?
No, there is not; see §3.2.4 “Compound Commands” in the Bash Reference Manual for information about the control structures that do exist. In particular, note the mention of break and continue, which aren’t as flexible as goto, but are more flexible in Bash than in some languages, and may help you achieve what you want. … Read more
How to convert a string to lower case in Bash?
The are various ways: POSIX standard tr AWK Non-POSIX You may run into portability issues with the following examples: Bash 4.0 sed Perl Bash Note: YMMV on this one. Doesn’t work for me (GNU bash version 4.2.46 and 4.0.33 (and same behaviour 2.05b.0 but nocasematch is not implemented)) even with using shopt -u nocasematch;. Unsetting that … Read more