#!/bin/sh
##apple soda
##banana split
##peach cobbler
##apple pie
##apple computer
##zuchinni casserole
##mango apple smoothie
##adam's apple
##app installer
##whatsapp
##application manager
export me=$0
datacmd="cat $me | grep ^##"
echo $datacmd
data=`$datacmd`
output:
Code:
beomagi@VBMagi ~ $ ./test.sh
cat ./test.sh | grep ^##
cat: |: No such file or directory
cat: grep: No such file or directory
cat: ^##: No such file or directory
The first line of the output
"cat ./test.sh | grep ^##" is from the line echo $datacmd
The next 3 lines of errors all come from this : data=`$datacmd`
Yet if I directly drop this into the prompt:
Code:
beomagi@VBMagi ~ $ cat ./test.sh | grep ^##
##apple soda
##banana split
##peach cobbler
##apple pie
##apple computer
##zuchinni casserole
##mango apple smoothie
##adam's apple
##app installer
##whatsapp
##application manager
It works.
i.e. cat ./test.sh | grep ^## works,
BUT if it's a in a string type variable and I execute it as a system call it barfs.
Why?
---------- Post updated at 09:33 PM ---------- Previous update was at 09:14 PM ----------
I'm balder now.
I think that helped.
I found out that there's "eval" and I can even call bash if i want to execute my string.
backticks just don't seem to cut it for complex calls.
Code:
#!/bin/sh
##apple soda
##banana split
##peach cobbler
##apple pie
##apple computer
##zuchinni casserole
##mango apple smoothie
##adam's apple
##app installer
##whatsapp
##application manager
datacmd="cat $me | grep ^##"
echo $datacmd
data=`eval "$datacmd"`
echo "$data"
gives:
Code:
beomagi@VBMagi ~ $ ./test.sh
cat ./test.sh | grep ^##
##apple soda
##banana split
##peach cobbler
##apple pie
##apple computer
##zuchinni casserole
##mango apple smoothie
##adam's apple
##app installer
##whatsapp
##application manager
Hi,
Ho do I differentiate system call from library call?
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Thanks
Muru (2 Replies)
hi,
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li v0, 4140
syscall
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Hi
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Discussion started by: VSSajjan
2 Replies
LEARN ABOUT DEBIAN
libbash
LIBBASH(7) libbash Manual LIBBASH(7)NAME
libbash -- A bash shared libraries package.
DESCRIPTION
libbash is a package that enables bash dynamic-like shared libraries. Actually its a tool for managing bash scripts whose functions you may
want to load and use in scripts of your own.
It contains a 'dynamic loader' for the shared libraries ( ldbash(1)), a configuration tool (ldbashconfig(8)), and some libraries.
Using ldbash(1) you are able to load loadable bash libraries, such as getopts(1) and hashstash(1). A bash shared library that can be loaded
using
ldbash(1) must answer 4 requirments:
1. It must be installed in $LIBBASH_PREFIX/lib/bash (default is /usr/lib/bash).
2. It must contain a line that begins with '#EXPORT='. That line will contain (after the '=') a list of functions that the library
exports. I.e. all the function that will be usable after loading that library will be listed in that line.
3. It must contain a line that begins with '#REQUIRE='. That line will contain (after the '=') a list of bash libraries that are
required for our library. I.e. every bash library that is in use in our bash library must be listed there.
4. The library must be listed (For more information, see ldbashconfig(8)).
Basic guidelines for writing library of your own:
1. Be aware, that your library will be actually sourced. So, basically, it should contain (i.e define) only functions.
2. Try to declare all variables intended for internal use as local.
3. Global variables and functions that are intended for internal use (i.e are not defined in '#EXPORT=') should begin with:
__<library_name>_
For example, internal function myfoosort of hashstash library should be named as
__hashstash_myfoosort
This helps to avoid conflicts in global name space when using libraries that come from different vendors.
4. See html manual for full version of this guide.
AUTHORS
Hai Zaar <haizaar@haizaar.com>
Gil Ran <ril@ran4.net>
SEE ALSO ldbash(1), ldbashconfig(8), getopts(1), hashstash(1)colors(1)messages(1)urlcoding(1)locks(1)Linux Epoch Linux
03-09-2015
