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Full Discussion: substitute a string on a specific position for specific lines
Top Forums Shell Programming and Scripting substitute a string on a specific position for specific lines Post 302480599 by ctsgnb on Wednesday 15th of December 2010 10:22:45 AM
Old 12-15-2010
@anurag

Ooops, you are true, i totally forgot that position case ... here is an even better
- need caret ^ to be exact regarding the position otherwise the \(.....<n_times>\)TOCHANGE could also be match at a position greater than the expected one
- use the $! tip to avoid last line)
- therefore avoid the use of additionnal file opening & line counting of the wc -l
- no need of sed -e option

Code:
sed '3s/^\(...........\)TOCHANGE\(.*\)/\1ABCABCAB\2/;$!{4,$s/^\(........\)TOCHANGE\(.*\)/\1ABCABCAB\2/}' infile

Code:
# cat tst1
12345678901TOCHANGE12345
12345678901TOCHANGE12345
12345678901TOCHANGE12345
12345678901TOCHANGE12345
12345678901TOCHANGE12345
12345678901TOCHANGE12345
12345678901TOCHANGE12345
# cat tst2
12345678TOCHANGE12345
12345678TOCHANGE12345
12345678TOCHANGE12345
12345678TOCHANGE12345
12345678TOCHANGE12345
12345678TOCHANGE12345
12345678TOCHANGE12345
# sed '3s/^\(...........\)TOCHANGE\(.*\)/\1ABCABCAB\2/;$!{4,$s/^\(........\)TOCHANGE\(.*\)/\1ABCABCAB\2/}' tst1
12345678901TOCHANGE12345
12345678901TOCHANGE12345
12345678901ABCABCAB12345
12345678901TOCHANGE12345
12345678901TOCHANGE12345
12345678901TOCHANGE12345
12345678901TOCHANGE12345
# sed '3s/^\(...........\)TOCHANGE\(.*\)/\1ABCABCAB\2/;$!{4,$s/^\(........\)TOCHANGE\(.*\)/\1ABCABCAB\2/}' tst2
12345678TOCHANGE12345
12345678TOCHANGE12345
12345678TOCHANGE12345
12345678ABCABCAB12345
12345678ABCABCAB12345
12345678ABCABCAB12345
12345678TOCHANGE12345

Last edited by ctsgnb; 12-15-2010 at 11:52 AM.. Reason: forgot the caret ^
 

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LEARN ABOUT MOJAVE

set_color

set_color(1)							       fish							      set_color(1)

NAME

       set_color - set_color - set the terminal color

set_color - set the terminal color
   Synopsis
       set_color [-v --version] [-h --help] [-b --background COLOR] [COLOR]

   Description
       Change the foreground and/or background color of the terminal. COLOR is one of black, red, green, brown, yellow, blue, magenta, purple,
       cyan, white and normal.

       o -b, --background Set the background color

       o -c, --print-colors Prints a list of all valid color names

       o -h, --help Display help message and exit

       o -o, --bold Set bold or extra bright mode

       o -u, --underline Set underlined mode

       o -v, --version Display version and exit

       Calling set_color normal will set the terminal color to whatever is the default color of the terminal.

       Some terminals use the --bold escape sequence to switch to a brighter color set. On such terminals, set_color white will result in a grey
       font color, while set_color --bold white will result in a white font color.

       Not all terminal emulators support all these features. This is not a bug in set_color but a missing feature in the terminal emulator.

       set_color uses the terminfo database to look up how to change terminal colors on whatever terminal is in use. Some systems have old and
       incomplete terminfo databases, and may lack color information for terminals that support it. Download and install the latest version of
       ncurses and recompile fish against it in order to fix this issue.

Version 1.23.1							  Sun Jan 8 2012						      set_color(1)
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