grep functions, how to test if succeeded Post: 302375469

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Top Forums Shell Programming and Scripting grep functions, how to test if succeeded Post 302375469 by gcampton on Friday 27th of November 2009 10:35:30 PM

11-27-2009

Banned

grep functions, how to test if succeeded

Hello ...again.
I am stuck on this part, I have a loop with processes an operations file.
and calls different functions depending on what is in loop, which processes a database file...

Code:

#so far my add function works as intended
add()
{
    ...blah blah;
}

# delete is kinda working havn't got all bugs out yet but have tested
# and played around with grep on test files, I have been able to delete
# a line from a file, but what i need it to do is
# search database for match product/brand if no such product exist then
# display error: product: not deleted does not exist
# else remove the record. So can delete it fine, but what I'm not sure of 
# is how to do the test to see if it exist first.
delete()
{
    grep -v "${1}:${2}" $dbfile > ../tmp/tmp
    sort ../tmp/tmp > $dbfile
}

#so what i need to do is test to see if the above command happened?
# i dunno :S

#i have to do the same thing with search functions, find product and find
# brand, both need to print error if they don't exist or, in case of find 
# brand it needs to print each line that matches. which I don't think will be 
# too difficult, just unsure of how to test.

gcampton

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LEARN ABOUT BSD

pipe

PIPE(2) 							System Calls Manual							   PIPE(2)

NAME

       pipe - create an interprocess communication channel

SYNOPSIS

       pipe(fildes)
       int fildes[2];

DESCRIPTION

       The pipe system call creates an I/O mechanism called a pipe.  The file descriptors returned can be used in read and write operations.  When
       the pipe is written using the descriptor fildes[1] up to 4096 bytes of data are buffered before the writing process is suspended.   A  read
       using the descriptor fildes[0] will pick up the data.

       It  is  assumed	that after the pipe has been set up, two (or more) cooperating processes (created by subsequent fork calls) will pass data
       through the pipe with read and write calls.

       The shell has a syntax to set up a linear array of processes connected by pipes.

       Read calls on an empty pipe (no buffered data) with only one end (all write file descriptors closed) returns an end-of-file.

       Pipes are really a special case of the socketpair(2) call and, in fact, are implemented as such in the system.

       A signal is generated if a write on a pipe with only one end is attempted.

RETURN VALUE

       The function value zero is returned if the pipe was created; -1 if an error occurred.

ERRORS

       The pipe call will fail if:

       [EMFILE]       Too many descriptors are active.

       [ENFILE]       The system file table is full.

       [EFAULT]       The fildes buffer is in an invalid area of the process's address space.

SEE ALSO

       sh(1), read(2), write(2), fork(2), socketpair(2)

BUGS

       Should more than 4096 bytes be necessary in any pipe among a loop of processes, deadlock will occur.

4th Berkeley Distribution					  August 26, 1985							   PIPE(2)

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