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Annotation of coherent/a/usr/man/COHERENT/trap, revision 1.1.1.1

1.1       root        1: 
                      2: 
                      3: trap                         Command                         trap
                      4: 
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                      6: 
                      7: 
                      8: Execute command on receipt of signal
                      9: 
                     10: ttrraapp [_c_o_m_m_a_n_d] [_n ...]
                     11: 
                     12: trap instructs the shell sh to execute the given command when the
                     13: shell receives signal n or any other signal in the optional list.
                     14: If the  command is omitted, trap resets traps  for the given sig-
                     15: nals to  the original  values.  If the  command is a  null string
                     16: (i.e., a  string that consists  only of one  null character), the
                     17: shell ignores  the given  signals.  If n  is zero, the  shell ex-
                     18: ecutes the  specified command when it exits.   When it is invoked
                     19: with no arguments, trap  prints the signal number and command for
                     20: each signal on which a trap is set.
                     21: 
                     22: The shell executes trap directly.
                     23: 
                     24: ***** Example *****
                     25: 
                     26: The  following example  takes two  files  and outputs  only those
                     27: lines which are the same.
                     28: 
                     29: 
                     30: # If input only one file-name then simply "cat".
                     31: if [ $# = 1 ]; then
                     32:         cat $1
                     33:         exit 0
                     34: 
                     35: 
                     36: 
                     37: # If input two file-names - Ok, else "Usage".
                     38: else
                     39:         if [ $# != 2 ]; then
                     40:                 echo "Usage: cmn file1 [file2]"
                     41:                 exit 1
                     42:         fi
                     43: fi
                     44: 
                     45: 
                     46: 
                     47: # TMP is original name of temporary file (/tmp/temp_(pid)
                     48: TMP=/tmp/temp_$$
                     49: 
                     50: 
                     51: 
                     52: # Temporary file has to be removed
                     53: trap 'rm $TMP; exit 1' 1 2 9
                     54: 
                     55: 
                     56: 
                     57: # Difference between "file1" and "difference between file1 and file2"
                     58: # is the common strings "file1" and "file2"
                     59: # The strings that are in "file1" and absent in "file2" print in TMP.
                     60: diff $1 $2 | sed -n -e "s/^< //p" > $TMP
                     61: 
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                     63: 
                     64: COHERENT Lexicon                                           Page 1
                     65: 
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                     67: 
                     68: 
                     69: trap                         Command                         trap
                     70: 
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                     73: 
                     74: 
                     75: # The strings that are in "file1" and absent in TMP print in stdout.
                     76: diff $1 $TMP | sed -n -e "s/^< //p"
                     77: 
                     78: 
                     79: 
                     80: # Remove temporary file
                     81: rm $TMP
                     82: 
                     83: 
                     84: ***** See Also *****
                     85: 
                     86: commands, sh, signal
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                    130: COHERENT Lexicon                                           Page 2
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