08-19-2010
Shell programming in Linux
Hi,
I have been working on Sun Solaris since a long time. Recently I got to work on RH Linux. My Linux version details are:
Linux 2.6.18-164.el5 #1 SMP Tue Aug 18 15:51:48 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux
I have a simple command in my shell script:
export BKPTAG=`date +"%Y%m%d_%H%M"`
This command does not get executed at all, and the error message is :
line 44: date: command not found
I tried executing the same command at Linux prompt and it gets executed very well.
my shell is /bin/bash and I have mentioned it as the first line in the shell script:
#!/bin/bash
This is very strange to me, can anyone throw light on this? Thanks in advance.
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GETCPU(2) Linux Programmer's Manual GETCPU(2)
NAME
getcpu - determine CPU and NUMA node on which the calling thread is running
SYNOPSIS
#include <linux/getcpu.h>
int getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache);
DESCRIPTION
The getcpu() system call identifies the processor and node on which the calling thread or process is currently running and writes them into
the integers pointed to by the cpu and node arguments. The processor is a unique small integer identifying a CPU. The node is a unique
small identifier identifying a NUMA node. When either cpu or node is NULL nothing is written to the respective pointer.
The third argument to this system call is nowadays unused.
The information placed in cpu is only guaranteed to be current at the time of the call: unless the CPU affinity has been fixed using
sched_setaffinity(2), the kernel might change the CPU at any time. (Normally this does not happen because the scheduler tries to minimize
movements between CPUs to keep caches hot, but it is possible.) The caller must be prepared to handle the situation when cpu and node are
no longer the current CPU and node.
VERSIONS
getcpu() was added in kernel 2.6.19 for x86_64 and i386.
CONFORMING TO
getcpu() is Linux specific.
NOTES
Linux makes a best effort to make this call as fast possible. The intention of getcpu() is to allow programs to make optimizations with
per-CPU data or for NUMA optimization.
Glibc does not provide a wrapper for this system call; call it using syscall(2); or use sched_getcpu(3) instead.
The tcache argument is unused since Linux 2.6.24. In earlier kernels, if this argument was non-NULL, then it specified a pointer to a
caller-allocated buffer in thread-local storage that was used to provide a caching mechanism for getcpu(). Use of the cache could speed
getcpu() calls, at the cost that there was a very small chance that the returned information would be out of date. The caching mechanism
was considered to cause problems when migrating threads between CPUs, and so the argument is now ignored.
SEE ALSO
mbind(2), sched_setaffinity(2), set_mempolicy(2), sched_getcpu(3), cpuset(7)
COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2008-06-03 GETCPU(2)