>
> Not if it succeeds.
> However, backtick -i will exit on error: you can use that difference in
> program flow to create the sequence you need.
I didn't find a construct where rest of the program can be executed in
same process as `backtick`, or at least forked after `backtick`.
Closest I could find is `ifte` with `backtick` as as `progif` and 2
copies of the remaining part of the program in `progif` and `progthen`
which is obviously ugly beyond any limits
>> backtick -n MAYBE_ARG { /bin/false }
>> import -u MAYBE_ARG
>> s6-echo ${MAYBE_ARG} $@
>
>
> Note that it's intentional that you always get an argument when
> expanding ${MAYBE_ARG}. That's a feature of execline.
Doesn't seem to be true, at least
```
import NOSUCHVAR
s6-echo ${NOSUCHVAR} $@
```
is equal to `s6-echo $@` if `NOSUCHVAR` is not an environment
variable. As you can see there is no explicit spitting, yet
`${NOSUCHVAR}` is substituted with no argument (not an empty
argument!)
>
>> I could add `-s` flag, to `import` and it solves problem for an empty
>> value,
>> but it also splits non empty value which is not desirable.
>
>
> Use a splitting delimiter that cannot appear in your value.
```
import -d "\0" -s
```
gives me a syntax error, anything else is just a magical value and I
am uncomfortable using it.
I can see that problem can be solved neatly with either:
1) introducing alternative to "cmd || :" shell construct, lets call it
`ignoreme` then it would be:
```
ignoreme backtick -i MAYBEARG { ... }
import -u MAYBEARG
...
```
but I can't see how it can be done in a model which execline follows.
It have to be like "foreground" but without a fork which seems not
doable.
2) introduce switch to a `backtick` which doesn't set variable on
subprocess error. Here is the patch I just prepared, it is completely
untested, didn't even try to compile yet, but would be happy to hear
feedback on approach
diff --git a/src/execline/backtick.c b/src/execline/backtick.c
index 2deb9f3..ae952c8 100644
--- a/src/execline/backtick.c
+++ b/src/execline/backtick.c
@@ -9,13 +9,13 @@
#include
#include
-#define USAGE "backtick [ -i | -D default ] [ -n ] var { prog... } command..."
+#define USAGE "backtick [ -i | -D default ] [ -z ] [ -n ] var { prog... } command..."
#define dieusage() strerr_dieusage(100, USAGE)
int main (int argc, char const *const *argv, char const *const *envp)
{
char const *def = 0 ;
- int insist = 0, chomp = 0 ;
+ int insist = 0, chomp = 0, skip_on_err = 0 ;
PROG = "backtick" ;
{
subgetopt_t l = SUBGETOPT_ZERO ;
@@ -29,6 +29,7 @@ int main (int argc, char const *const *argv, char const *const *envp)
case 'n' : chomp = 1 ; break ;
case 'i' : insist = 1 ; break ;
case 'D' : def = l.arg ; break ;
+case 'z' : zkip_on_err = 1; break ;
default : dieusage() ;
}
}
@@ -57,6 +58,7 @@ int main (int argc, char const *const *argv, char const *const *envp)
newargv[m++] = EXECLINE_BINPREFIX "withstdinas" ;
if (insist) newargv[m++] = "-i" ;
if (chomp) newargv[m++] = "-n" ;
+if (skip_on_err) newargv[m++] = "-z" ;
if (def)
{
newargv[m++] = "-D" ;
diff --git a/src/execline/withstdinas.c b/src/execline/withstdinas.c
index c1e3c36..29a876c 100644
--- a/src/execline/withstdinas.c
+++ b/src/execline/withstdinas.c
@@ -17,8 +17,8 @@ int main (int argc, char const **argv, char const *const *envp)
{
subgetopt_t localopt = SUBGETOPT_ZERO ;
stralloc modif = STRALLOC_ZERO ;
- unsigned int modifstart ;
- int insist = 0, chomp = 0, reapit = 0 ;
+ unsigned int modifstart = 0 ;
+ int insist = 0, chomp = 0, reapit = 0 , skip_on_err = 0 ;
char const *def = 0 ;
PROG = "withstdinas" ;
for (;;)
@@ -31,6 +31,7 @@ int main (int argc, char const **argv, char const *const *envp)
case 'n' : chomp = 1 ; break ;
case 'D' : def = localopt.arg ; break ;
case '!' : reapit = 1 ; break ;
+ case 'z' : skip_on_err = 1 ; break ;
default : dieusage() ;
}
}
@@ -56,7 +57,9 @@ int main (int argc, char const **argv, char const *const *envp)
strerr_diefu1sys(111, "waitpid") ;
if (wait_estatus(wstat))
{
-if (insist)
+if (skip_on_err)
+ modif.len = 2
+else if (insist)
if (WIFSIGNALED(wstat)) strerr_dief1x(wait_estatus(wstat), "child process crashed") ;
else strerr_dief1x(wait_estatus(wstat), "child process exited non-zero") ;
else if (def)
