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From: Dominic Fandrey on 23 Feb 2010 04:39 Some of my shell scripts need to invoke a new shell (e.g. when using lockf(1) ). To get the interpreting shell, I use: interpreter="$(ps -o command -p $$ | tail -n1 | sed "s, $0${*:+ $*}\$,,1")" This will yield whatever shell I used to invoke the script on FreeBSD, e.g. "/bin/sh -f" or "bash". I wonder whether this is portable, i.e. whether it works on other systems.
From: Kenny McCormack on 23 Feb 2010 07:28 In article <hm07pf$f41$1(a)news.doubleSlash.org>, Dominic Fandrey <kamikaze(a)bsdforen.de> wrote: >Some of my shell scripts need to invoke a new shell (e.g. when using >lockf(1) ). > >To get the interpreting shell, I use: >interpreter="$(ps -o command -p $$ | tail -n1 | sed "s, $0${*:+ $*}\$,,1")" > >This will yield whatever shell I used to invoke the script on FreeBSD, e.g. >"/bin/sh -f" or "bash". > >I wonder whether this is portable, i.e. whether it works on other systems. As you can probably see yourself, anything like that - that depends on ps and the various other utilities - cannot be proven portable. Now, of course, the standards jockeys will come in and say that "POSIX requires blah, blah, blah", but the fact is that "ps" is known to be one of those loopy utilities that just can't be assumed to be standardized (or predictable). If what you are really trying to do is distinguish 'sh' from 'bash', then I think there are documented "feature test" type solutions - check for some environment variable or something that (in the most likely case) 'bash' supplies, but is missing in 'sh'. I think that's the way to go. A little bit of googling will probably reveal a complete test suite - to test for all the common shells.
From: Dominic Fandrey on 23 Feb 2010 12:17 On 23/02/2010 13:28, Kenny McCormack wrote: > In article <hm07pf$f41$1(a)news.doubleSlash.org>, > Dominic Fandrey <kamikaze(a)bsdforen.de> wrote: >> Some of my shell scripts need to invoke a new shell (e.g. when using >> lockf(1) ). >> >> To get the interpreting shell, I use: >> interpreter="$(ps -o command -p $$ | tail -n1 | sed "s, $0${*:+ $*}\$,,1")" >> >> This will yield whatever shell I used to invoke the script on FreeBSD, e.g. >> "/bin/sh -f" or "bash". >> >> I wonder whether this is portable, i.e. whether it works on other systems. > > As you can probably see yourself, anything like that - that depends on > ps and the various other utilities - cannot be proven portable. Now, of > course, the standards jockeys will come in and say that "POSIX requires > blah, blah, blah", but the fact is that "ps" is known to be one of those > loopy utilities that just can't be assumed to be standardized (or > predictable). Hmm, I see that. I need to use interpreter="$(ps -o args -p $$ | tail -n1 | sed "s, $0${*:+ $*}\$,,1")" to yield the desired results on AIX (luckily this version also works on FreeBSD). > If what you are really trying to do is distinguish 'sh' from 'bash', > then I think there are documented "feature test" type solutions - check > for some environment variable or something that (in the most likely > case) 'bash' supplies, but is missing in 'sh'. I think that's the way > to go. A little bit of googling will probably reveal a complete test > suite - to test for all the common shells. I also need to know the parameters, so that a lockf lockfile $interpreter -c "..." forwards parameters like -x (for debugging). -- A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing on usenet and in e-mail?
From: Stephane CHAZELAS on 23 Feb 2010 12:23 2010-02-23, 10:39(+01), Dominic Fandrey: > Some of my shell scripts need to invoke a new shell (e.g. when using > lockf(1) ). > > To get the interpreting shell, I use: > interpreter="$(ps -o command -p $$ | tail -n1 | sed "s, $0${*:+ $*}\$,,1")" > > This will yield whatever shell I used to invoke the script on FreeBSD, e.g. > "/bin/sh -f" or "bash". > > I wonder whether this is portable, i.e. whether it works on other systems. ps -o args= -p "$$" ps -o comm= -p "$$" would be POSIX. -- St�phane
From: Dominic Fandrey on 23 Feb 2010 12:28
On 23/02/2010 18:23, Stephane CHAZELAS wrote: > 2010-02-23, 10:39(+01), Dominic Fandrey: >> Some of my shell scripts need to invoke a new shell (e.g. when using >> lockf(1) ). >> >> To get the interpreting shell, I use: >> interpreter="$(ps -o command -p $$ | tail -n1 | sed "s, $0${*:+ $*}\$,,1")" >> >> This will yield whatever shell I used to invoke the script on FreeBSD, e.g. >> "/bin/sh -f" or "bash". >> >> I wonder whether this is portable, i.e. whether it works on other systems. > > ps -o args= -p "$$" > ps -o comm= -p "$$" > > would be POSIX. > Oh great, so I don't need tail to get rid of the header! Thanks! -- A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing on usenet and in e-mail? |