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Shell Programming and Scripting
redirect an awk string output to a script input with pipes
Post 302383211 by alister on Monday 28th of December 2009 09:32:25 PM
12-28-2009
It seems you are conflating pipes and command line options. They are unrelated concepts.
A pipe redirects the standard output of one command into the standard input of another. To read what is being sent in via a pipe, a process has to read from standard input using file i/o.
Command line options are usually made available to a program/script through an array (argv for C executables) or special variables ($*, $@, $1, $2, etc) for shell scripts. getopt (a function in the C library and a command for shell script use) is used to process the command line options.
These are two different mechanisms for passing information. If you want to pass what is in param2 in via a pipe, myscript.sh would have to read it from its stdin. However, it's probably using the variable $2 as it expects it on the command line.
Hopefully that helps clear it up. If not, perhaps it's a start.
Take care,
alister
A pipe redirects the standard output of one command into the standard input of another. To read what is being sent in via a pipe, a process has to read from standard input using file i/o.
Command line options are usually made available to a program/script through an array (argv for C executables) or special variables ($*, $@, $1, $2, etc) for shell scripts. getopt (a function in the C library and a command for shell script use) is used to process the command line options.
These are two different mechanisms for passing information. If you want to pass what is in param2 in via a pipe, myscript.sh would have to read it from its stdin. However, it's probably using the variable $2 as it expects it on the command line.
Hopefully that helps clear it up. If not, perhaps it's a start.
Take care,
alister
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LEARN ABOUT OPENDARWIN
pipe
PIPE(2) BSD System Calls Manual PIPE(2) NAME
pipe -- create descriptor pair for interprocess communication SYNOPSIS
#include <unistd.h> int pipe(int *fildes); DESCRIPTION
The pipe() function creates a pipe, which is an object allowing unidirectional data flow, and allocates a pair of file descriptors. The first descriptor connects to the read end of the pipe, and the second connects to the write end, so that data written to fildes[1] appears on (i.e., can be read from) fildes[0]. This allows the output of one program to be sent to another program: the source's standard output is set up to be the write end of the pipe, and the sink's standard input is set up to be the read end of the pipe. The pipe itself persists until all its associated descriptors are closed. A pipe whose read or write end has been closed is considered widowed. Writing on such a pipe causes the writing process to receive a SIGPIPE signal. Widowing a pipe is the only way to deliver end-of-file to a reader: after the reader consumes any buffered data, reading a widowed pipe returns a zero count. RETURN VALUES
On successful creation of the pipe, zero is returned. Otherwise, a value of -1 is returned and the variable errno set to indicate the error. 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) HISTORY
A pipe() function call appeared in Version 6 AT&T UNIX. 4th Berkeley Distribution June 4, 1993 4th Berkeley Distribution