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Shell Programming and Scripting
Relacing the shebang line of a file
Post 302271294 by linuxnewbe on Wednesday 24th of December 2008 06:55:50 PM
12-24-2008
Thank you for your prompt reply 
and it helps me to proceed further. But still I am missing some thing.
Output of the command " sed "s%$(head -1 file1.txt)%#\!$(which ruby)%g" file1.txt " is displaying the modified shebang line along with the contents of the file on the console. But if I pass the o/p using tee operator to the same file the whole contents of the file has been lost.
command:
sed "s%$(head -1 file1.txt)%#\!$(which ruby)%g" file1.txt | tee file1.txt
So I have found a work around to pass the o/p of the command "sed "s%$(head -1 file1.txt)%#\!$(which ruby)%g" file1.txt" to a temparary file and then copying the contents of the temparary file to the original.
command:
sed "s%$(head -1 file1.txt)%#\!$(which ruby)%g" file1.txt | tee file2.txt
cp file2.txt file1.txt
Is there any way I can accomplish the whole task from a single sed command?
and it helps me to proceed further. But still I am missing some thing. Output of the command " sed "s%$(head -1 file1.txt)%#\!$(which ruby)%g" file1.txt " is displaying the modified shebang line along with the contents of the file on the console. But if I pass the o/p using tee operator to the same file the whole contents of the file has been lost.
command:
sed "s%$(head -1 file1.txt)%#\!$(which ruby)%g" file1.txt | tee file1.txt
So I have found a work around to pass the o/p of the command "sed "s%$(head -1 file1.txt)%#\!$(which ruby)%g" file1.txt" to a temparary file and then copying the contents of the temparary file to the original.
command:
sed "s%$(head -1 file1.txt)%#\!$(which ruby)%g" file1.txt | tee file2.txt
cp file2.txt file1.txt
Is there any way I can accomplish the whole task from a single sed command?
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LEARN ABOUT OPENSOLARIS
comm
comm(1) User Commands comm(1) NAME
comm - select or reject lines common to two files SYNOPSIS
comm [-123] file1 file2 DESCRIPTION
The comm utility reads file1 and file2, which must be ordered in the current collating sequence, and produces three text columns as output: lines only in file1; lines only in file2; and lines in both files. If the input files were ordered according to the collating sequence of the current locale, the lines written will be in the collating sequence of the original lines. If not, the results are unspecified. OPTIONS
The following options are supported: -1 Suppresses the output column of lines unique to file1. -2 Suppresses the output column of lines unique to file2. -3 Suppresses the output column of lines duplicated in file1 and file2. OPERANDS
The following operands are supported: file1 A path name of the first file to be compared. If file1 is -, the standard input is used. file2 A path name of the second file to be compared. If file2 is -, the standard input is used. USAGE
See largefile(5) for the description of the behavior of comm when encountering files greater than or equal to 2 Gbyte ( 2^31 bytes). EXAMPLES
Example 1 Printing a list of utilities specified by files If file1, file2, and file3 each contain a sorted list of utilities, the command example% comm -23 file1 file2 | comm -23 - file3 prints a list of utilities in file1 not specified by either of the other files. The entry: example% comm -12 file1 file2 | comm -12 - file3 prints a list of utilities specified by all three files. And the entry: example% comm -12 file2 file3 | comm -23 -file1 prints a list of utilities specified by both file2 and file3, but not specified in file1. ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables that affect the execution of comm: LANG, LC_ALL, LC_COLLATE, LC_CTYPE, LC_MESSAGES, and NLSPATH. EXIT STATUS
The following exit values are returned: 0 All input files were successfully output as specified. >0 An error occurred. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWesu | +-----------------------------+-----------------------------+ |CSI |enabled | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ SEE ALSO
cmp(1), diff(1), sort(1), uniq(1), attributes(5), environ(5), largefile(5), standards(5) SunOS 5.11 3 Mar 2004 comm(1)