If you want the script to abort if there are any invalid variable names in the config (if you try the following, with an invalid variable name in config, in your current shell, it will *poof* disappear , so make sure to do it in a subshell):
Code:
set -e
. config_file
set +e
Or, you could leave "set -e" on, if you like (it causes the shell to terminate when a command fails, with certain exceptions regarding and-or lists and conditionals ... read your shell's 'set' documentation for more info).
As to spaces in a pathname, I don't see how you can detect them since you are using spaces to delimit each path. How is the code to know if the space is embedded in a path or meant to separate one path from another? To be absolutely certain of whether a character is in a path or a delimiter, you would need to select a delimiter that cannot occur in a UNIX path. There is only one such character, the null byte, and it's notoriously difficult to work with in most shells. Perhaps simply checking the validity of each path is sufficient.
Assuming that the config file was sourced as in my example above (using the dot command):
Code:
for p in $PATHS_TO_WATCH; do
if [ ! -d $p ]; then
echo $0: $p: bad path 1>&2
exit 1
fi
done
If an invalid path is encountered, a message (including the script's name and the offending path) is printed to standard error and an exit status of 1 is returned.
Herez the question,
In a process which writes into file FILE1 with descriptor
fHandler1 and it is run as a background process
where would statements be directed
when stderr descriptor is used.
fprintf(stderr,"some message\n");
assume that session from which it is run is terminated and... (3 Replies)
can pipe sychronize thread or process? because I'm trying to create 5 thread or process that can take an integer value and display it. each time a thread display the value, it has to be decrement it by 1 until the value has reach 0. The problem that I'm having is how can that integer value be... (1 Reply)
I have the following code which works on AIX 4.3 but fails at times on AIX 5.3
with:
cat: 0652-054 cannot write to output. There is no process to read data written to a pipe.
validator="${validator_exe} ${validator_parms}"
cmd_line="${CAT} ${data_file} | ${validator}... (6 Replies)
Hi folks :)
Can deamonized process access to stderr, stdout?
I 'm trying to display error_num/return value of a function run() in stderr using
fprintf(stderr, "function run() returns = %d", ret_val);
run() is called after deamonizing the process. (1 Reply)
Hi.. I am hoping someone could assist me with the pipe program I wrote below. I want to have communication from parent to child and then child to parent.. Is my logic right?
int p,p1;
pipe(p);
pipe(p1);
pid_t pid = fork();
if(pid == 0)
{
close(p);
close(p1);
dup2(p,0);... (1 Reply)
Hi Everyone,
The machine I'm working on is an AIX 5.3 LPAR running on a P650. oslevel -r shows 5300-08. I'm trying to take a backup to a SCSI tape drive, which has been working up until this point. I know of nothing that has changed recently to cause this problem. But when I try to take a... (0 Replies)
We use SAP application cluster on AIX. Communication between 2 of its instances is failing randomly with the following error:
java.net.SocketException: There is no process to read data written to a pipe.
The above error causes a cluster restart if an important communication fails.
Can... (0 Replies)
Hi,
I've came across an issue with a script I've been writing to check DHCP addresses on an Solaris system, the script has been running reasonably well, until it hit the following problem:
./sub_mon_v2: redirection error: cannot duplicate fd: Too many open files
./sub_mon_v2: cannot make... (3 Replies)
Dear all,
I use a pipe command to assign a variable:
$ v_LstStdCdhId=$(cat Bteq_Xport_GetLstStdViewToBuild__1274.txt | grep 'CD/39/AT/CDH_BV_ODS'|cut -d"/" -f1)
$ echo "${v_LstStdCdhId}"
43
49
My aim is to concatenate for each line of the variable v_LstStdCdhId the character "/" in... (3 Replies)
Discussion started by: dae
3 Replies
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)
04-21-2010
, so make sure to do it in a subshell):