05-21-2008
eval in shell scripting
what is the real usage of eval in shell scripting
whats the difference between
$ cmd
&&
eval cmd
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Linux s10-1310 2.6.16.53-0.8.PTF.434477.3.TDC.0-smp #1 SMP Fri Aug 31 06:07:27 PDT 2007 x86_64 x86_64 x86_64 GNU/Linux
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anyone has any info on why this is complaining???
vivek@vivek-c5e55ef2e ~/TAC
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$ optUsage1=23%
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anyone has any info on why this is complaining???
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LEARN ABOUT DEBIAN
plan9-getflags
GETFLAGS(8) System Manager's Manual GETFLAGS(8)
NAME
getflags, usage - command-line parsing for shell scripts
SYNOPSIS
getflags $*
usage [ progname ]
DESCRIPTION
Getflags parses the options in its command-line arguments according to the environment variable $flagfmt. This variable should be a list
of comma-separated options. Each option can be a single letter, indicating that it does not take arguments, or a letter followed by the
space-separated names of its arguments. Getflags prints an rc(1) script on standard output which initializes the environment variable
$flagx for every option mentioned in $flagfmt. If the option is not present on the command-line, the script sets that option's flag vari-
able to an empty list. Otherwise, the script sets that option's flag variable with a list containing the option's arguments or, if the
option takes no arguments, with the string 1. The script also sets the variable $* to the list of arguments following the options. The
final line in the script sets the $status variable, to the empty string on success and to the string usage when there is an error parsing
the command line.
Usage prints a usage message to standard error. It creates the message using $flagfmt, as described above, $args, which should contain the
string to be printed explaining non-option arguments, and $0, the program name (see rc(1)). If run under sh(1), which does not set $0, the
program name must be given explicitly on the command line.
EXAMPLE
Parse the arguments for leak(1):
flagfmt='b,s,f binary,r res,x width'
args='name | pid list'
if(! ifs=() eval `{getflags $*} || ~ $#* 0){
usage
exit usage
}
SOURCE
/src/cmd/getflags.c
/src/cmd/usage.c
SEE ALSO
arg(3)
GETFLAGS(8)