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Full Discussion: sed doubt in extracting
Top Forums Shell Programming and Scripting sed doubt in extracting Post 302427847 by pludi on Tuesday 8th of June 2010 05:54:48 AM
Old 06-08-2010
Code:
s/[^x]//g

This means "replace the first character which isn't a 'x' with nothing". Since that's done as soon as the first 't' is replaced, sed is finished. If you want to remove all characters leading up to the first 'x', use
Code:
s/[^x]*//g

In the second snipped:
Code:
echo 'x_a_b_a_c_a_d' | sed 's/.*\(a\)/\1/'

you're replacing as many characters as possible from the start until the last possible 'a' with the matched 'a'. The rest of the string isn't affected, so 'x_a_b_a_c_a' is replaced by 'a', which changes 'x_a_b_a_c_a_d' to 'a_d'

Third:
Code:
echo 'foo-bar-1.4.5-19.spkg' | sed 's/-[^-]*$//'

means "starting with a dash, take as many non-dash characters as possible until the end, and replace them with nothing", or "remove everything starting from and including the last possible dash".
 

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Tk_GetDash(3)						       Tk Library Procedures						     Tk_GetDash(3)

__________________________________________________________________________________________________________________________________________________

NAME
Tk_GetDash - convert from string to valid dash structure. SYNOPSIS
#include <tk.h> int Tk_GetDash(interp, string, dashPtr) ARGUMENTS
Tcl_Interp *interp (in) Interpreter to use for error reporting. const char * string (in) Textual value to be converted. Tk_Dash *dashPtr (out) Points to place to store the dash pattern value converted from string. _________________________________________________________________ DESCRIPTION
These procedure parses the string and fills in the result in the Tk_Dash structure. The string can be a list of integers or a character string containing only ".,-_" or spaces. If all goes well, TCL_OK is returned. If string does not have the proper syntax then TCL_ERROR is returned, an error message is left in the interpreter's result, and nothing is stored at *dashPtr. The first possible syntax is a list of integers. Each element represents the number of pixels of a line segment. Only the odd segments are drawn using the "outline" color. The other segments are drawn transparent. The second possible syntax is a character list containing only 5 possible characters ".,-_ ". The space can be used to enlarge the space between other line elements, and can not occur as the first position in the string. Some examples: -dash . = -dash {2 4} -dash - = -dash {6 4} -dash -. = -dash {6 4 2 4} -dash -.. = -dash {6 4 2 4 2 4} -dash {. } = -dash {2 8} -dash , = -dash {4 4} The main difference of this syntax with the previous is that it is shape-conserving. This means that all values in the dash list will be multiplied by the line width before display. This assures that "." will always be displayed as a dot and "-" always as a dash regardless of the line width. On systems where only a limited set of dash patterns, the dash pattern will be displayed as the most close dash pattern that is available. For example, on Windows only the first 4 of the above examples are available. The last 2 examples will be displayed identically as the first one. KEYWORDS
dash, conversion Tk 8.3 Tk_GetDash(3)
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