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Top Forums Shell Programming and Scripting Checking and replacing first line in text file, one-liner? Post 303015315 by f77hack on Monday 2nd of April 2018 05:51:10 PM
Old 04-02-2018
Checking and replacing first line in text file, one-liner?

Hello,
I'm looking to check only the first line of a file to see if it is a format string, like

Code:
# -*- coding: utf-8; mode: tcl; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -\*- vim:fenc=utf-8:ft=tcl:et:sw=2:ts=2:sts=2

if the first line is anything else, insert the above string.

I'd appreciate a one liner as I'm putting this command inside of a

Code:
find . -depth -name "*.tcl" -type f -writeable ! -executable -exec awk INSERT_COOL_LINER

so far I'm hacking awk that looks like
Code:
awk 'NR==1 && /^#./ {print "format string exists";exit 1} {print "no format string";exit 1}' test.tcl

which correctly detects if the format string is there or not but can't seem to figure out how to get awk to redirect the pipe to insert the format string?

Thanks
 

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fspec(4)						     Kernel Interfaces Manual							  fspec(4)

NAME
fspec - format specification in text files DESCRIPTION
It is sometimes convenient to maintain text files on the HP-UX system with non-standard tabs, (meaning tabs that are not set at every eighth column). Generally, such files must be converted to a standard format - frequently by replacing all tabs with the appropriate num- ber of spaces - before they can be processed by HP-UX system commands. A format specification occurring in the first line of a text file specifies how tabs are to be expanded in the remainder of the file. A format specification consists of a sequence of parameters separated by blanks and surrounded by the brackets and Each parameter consists of a keyletter, possibly followed immediately by a value. The following parameters are recognized: The parameter specifies tab settings for the file. The value of tabs must be one of the following: 1. A list of column numbers separated by commas, indicating tabs set at the specified columns; 2. A followed immediately by an integer n, indicating tabs at intervals of n columns; 3. A followed by the name of a ``canned'' tab specification. Standard tabs are specified by or equivalently, etc. Recognized canned tabs are defined by the command (see tabs(1)). The parameter specifies a maximum line size. The value of size must be an integer. Size checking is performed after tabs have been expanded, but before the margin is inserted at the beginning of the line. The parameter specifies a number of spaces to be inserted at the beginning of each line. The value of margin must be an integer. The parameter takes no value. Its presence indicates that the line containing the format specification is to be deleted from the converted file. The parameter takes no value. Its presence indicates that the current format is to prevail only until another format specification is encountered in the file. Default values (assumed for parameters not supplied) are and If the parameter is not specified, no size checking is performed. If the first line of a file does not contain a format specification, the above defaults are assumed for the entire file. The following is an example of a line containing a format specification: If a format specification can be disguised as a comment, it is not necessary to code the parameter. Several HP-UX system commands correctly interpret the format specification for a file. Among them is which can be used to convert files to a standard format acceptable to other HP-UX system commands. SEE ALSO
ed(1), newform(1), tabs(1). fspec(4)
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