On 2012-02-26 09:20, Adam D. Barratt wrote:
| On Sun, 2012-02-26 at 03:30 +0100, Jakub Wilk wrote:
| > * Jari Aalto <[email protected]>, 2012-02-08, 02:58:
| > >- [ "`head -n 1 \"$1\"`" = "-----BEGIN PGP SIGNED MESSAGE-----" ] || \
| > >+ [ "$(head -n 1 \"$1\")" = "-----BEGIN PGP SIGNED MESSAGE-----" ] || \
| >
| > Bzzt, wrong.
| >
| > $ foo=/etc/ld.so.conf; echo "`head -n 1 \"$foo\"`"
| > include /etc/ld.so.conf.d/*.conf
| >
| > $ foo=/etc/ld.so.conf; echo "$(head -n 1 \"$1\")"
| > head: cannot open `""' for reading: No such file or directory
|
| fwiw, it breaks even if you remember to use the right variable in the
| second example... ;-)
|
| $ foo=/etc/ld.so.conf; echo "$(head -n 1 \"$foo\")"
| head: cannot open `"/etc/ld.so.conf"' for reading: No such file or directory
One of the benfits of POSIX command substitution is also, that there
is no need for extra quoting:
$ foo=/etc/ld.so.conf; echo "$(head -n 1 "$foo")"
include /etc/ld.so.conf.d/*.conf
The $() is interepreted first, so the echo quotes are not affected.
Jari
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