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Full Discussion: sed command - substitue first instance
Top Forums Shell Programming and Scripting sed command - substitue first instance Post 302070374 by d_swapneel14 on Tuesday 4th of April 2006 11:13:08 AM
Old 04-04-2006
sed command - substitue first instance
hi


i have one file where i want to substitute only first instance of
swap
with swap1
i want to replcae only first instance of swap in my script

i know we can do this with awk. but i need to do this with sed only

i tried follwoing code
sed 's/swap/swap1' filename

but here all swap will get replaced with swap1

i want to replace only one and first instance of swap

plz guide me

Thank You
Best Regards,
Swapneel
 

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LEARN ABOUT MOJAVE

swap

swap(1M)                                                  System Administration Commands                                                  swap(1M)

NAME

       swap - swap administrative interface

SYNOPSIS

       /usr/sbin/swap -a swapname [swaplow] [swaplen]

       /usr/sbin/swap -d swapname [swaplow]

       /usr/sbin/swap -l

       /usr/sbin/swap -s

DESCRIPTION

       The swap utility provides a method of adding, deleting, and monitoring the system swap areas used by the memory manager.

OPTIONS

       The following options are supported:

       -a swapname     Add  the  specified  swap  area. This option can only be used by the super-user. swapname is the name of the swap file: for
                       example, /dev/dsk/c0t0d0s1 or a regular file. swaplow is the offset in 512-byte blocks into the file where  the  swap  area
                       should  begin. swaplen is the desired length of the swap area in 512-byte blocks. The value of swaplen can not be less than
                       16. For example, if n blocks are specified, then (n-1) blocks would be the actual swap length. swaplen must be at least one
                       page  in  length.  The size of a page of memory can be determined by using the pagesize command. See pagesize(1). Since the
                       first page of a swap file is automatically skipped, and a swap file needs to be at least one page in  length,  the  minimum
                       size should be a multiple of 2 pagesize bytes. The size of a page of memory is machine dependent.

                       swaplow  +  swaplen  must  be less than or equal to the size of the swap file. If swaplen is not specified, an area will be
                       added starting at swaplow and extending to the end of the designated file. If neither swaplow nor  swaplen  are  specified,
                       the whole file will be used except for the first page. Swap areas are normally added automatically during system startup by
                       the /sbin/swapadd script. This script adds all swap areas which have been specified in the /etc/vfstab file; for the syntax
                       of these specifications, see vfstab(4).

                       To use an NFS or local file-system swapname, you should first create a file using mkfile(1M). A local file-system swap file
                       can now be added to the running system by just running the swap -a command. For NFS mounted swap files, the server needs to
                       export the file. Do this by performing the following steps:

                           1.  Add the following line to /etc/dfs/dfstab:

                               share -F nfs -o rw=clientname,root=clientname path-to-swap-file

                           2.  Run shareall(1M).

                           3.  Have the client add the following line to /etc/vfstab:

                               server:path-to-swap-file -  local-path-to-swap-filenfs 
                                    --- local-path-to-swap-file -- swap ---

                           4.  Have the client run mount:

                               # mount local-path-to-swap-file

                           5.  The client can then run swap -a to add the swap space:

                               # swap -a  local-path-to-swap-file

       -d swapname     Delete  the specified swap area. This option can only be used by the super-user. swapname is the name of the swap file: for
                       example, /dev/dsk/c0t0d0s1 or a regular file. swaplow is the offset in 512-byte blocks into the swap area to be deleted. If
                       swaplow is not specified, the area will be deleted starting at the second page. When the command completes, swap blocks can
                       no longer be allocated from this area and all swap blocks previously in use in this swap area have been moved to other swap
                       areas.

       -l              List the status of all the swap areas. The output has five columns:

                       path     The path name for the swap area.

                       dev      The major/minor device number in decimal if it is a block special device; zeroes otherwise.

                       swaplo   The swaplow value for the area in 512-byte blocks.

                       blocks   The swaplen value for the area in 512-byte blocks.

                       free     The number of 512-byte blocks in this area that are not currently allocated.

                       The  list does not include swap space in the form of physical memory because this space is not associated with a particular
                       swap area.

                       If swap -l is run while swapname is in the process of being deleted (by swap -d), the string INDEL will appear in  a  sixth
                       column of the swap stats.

       -s              Print summary information about total swap space usage and availability:

                       allocated       The total amount of swap space in bytes currently allocated for use as backing store.

                       reserved        The  total amount of swap space in bytes not currently allocated, but claimed by memory mappings for possi-
                                       ble future use.

                       used            The total amount of swap space in bytes that is either allocated or reserved.

                       available       The total swap space in bytes that is currently available for future reservation and allocation.

                       These numbers include swap space from all configured swap areas as listed by the -l option, as well swap space in the  form
                       of physical memory.

USAGE

       On  the  32-bit  operating  system,  only the first 2 Gbytes -1 are used for swap devices greater than or equal to 2 Gbytes in size. On the
       64-bit operating system, a block device larger than 2 Gbytes can be fully utilized for swap up to 2**63 -1 bytes.

ENVIRONMENT VARIABLES

       See environ(5) for descriptions of the following environment variables that affect the execution of swap: LC_CTYPE and LC_MESSAGE.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE         |      ATTRIBUTE VALUE        |
       +-----------------------------+-----------------------------+
       |Availability                 |SUNWcsu                      |
       +-----------------------------+-----------------------------+

SEE ALSO

       pagesize(1), mkfile(1M), shareall(1M), getpagesize(3C), vfstab(4),  attributes(5), largefile(5)

WARNINGS

       No check is done to determine if a swap area being added overlaps with an existing file system.

SunOS 5.10                                                          20 Jan 2004                                                           swap(1M)
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