{"id":125,"date":"2005-11-04T14:51:00","date_gmt":"2005-11-04T14:51:00","guid":{"rendered":"http:\/\/adam.rosi-kessel.org\/weblog\/free_software\/code\/randomplay_0.48_released.html"},"modified":"-0001-11-30T00:00:00","modified_gmt":"1970-01-01T05:00:00","slug":"randomplay_048_released","status":"publish","type":"post","link":"http:\/\/adam.rosi-kessel.org\/weblog\/2005\/11\/04\/randomplay_048_released","title":{"rendered":"randomplay 0.48 released"},"content":{"rendered":"

I’ve released randomplay 0.48<\/a>. randomplay<\/a> is my command-line ‘itch a scratch’ music player. It is most useful for maintaining a random shuffle over many sessions—for example, I use it to make sure I don’t ever hear the same song in any three month period. <\/p>\n

The new version fixes a bug that prevented randomplay from advancing to the next track when the player subprocess itself spawned a child process (e.g., with ‘play’ which spawns ‘sox’). I use a bit of a hack to kill the child task and it’s children, but the standard way of doing this in perl—kill HUP => -$$ doesn’t seem to work when randomplay is called from a shell script and the child process’ output is redirected to null. Here’s the code in question (with the fix to kill children and grandchildren recursively): <\/p>\n

 # KillAll recursively kills the request process ID and all of its children\/grandchildren\/etc. # This is a bit of a hack--there should be a better way to do this, but I haven't found one. # Normally, kill HUP => -$$ should do the job, except this doesn't work when randomplay itself # is called from a shell script and all output from child processes is redirected to null. # This subroutine assumes that shelling out to ps is going to work, which may not be totally # safe--at the very least, it reduces the portability of the script. # Any suggestions for a better way to do this are welcome. <\/font>sub KillAll<\/font> {<\/strong> my<\/strong> $pid<\/font> = shift<\/strong><\/font>; local<\/strong> $SIG<\/font>{<\/strong><\/font>HUP}<\/strong><\/font> = 'IGNORE'<\/font>; # don't want to kill ourselves here--shouldn't happen, but just in case. <\/font>if<\/strong> (<\/strong><\/font>open<\/strong><\/font> PS, \"ps -o pid,ppid |\"<\/font>)<\/strong><\/font> {<\/strong><\/font> eof<\/strong><\/font> PS; # Force ps to run now. Otherwise it would run at the first read operation. <\/font>kill<\/strong><\/font> HUP => $pid<\/font>; foreach<\/strong> my<\/strong> $line<\/font> (<\/strong><\/font>)<\/strong><\/font> {<\/strong><\/font> KillAll(<\/strong><\/font>$1<\/font>)<\/strong><\/font> if<\/strong> (<\/strong><\/font>$line<\/font> =~ \/^\\s*(\\d+)\\s*(\\d+)\\s*$\/<\/font> and<\/strong> (<\/strong><\/font>$2<\/font> eq<\/strong> $pid<\/font>)<\/strong><\/font>)<\/strong><\/font>; }<\/strong><\/font> close<\/strong><\/font> PS; }<\/strong><\/font> else<\/strong> {<\/strong><\/font> # if we can't read the process table, just try killing the child process group <\/font>kill<\/strong><\/font> HUP => -$$;<\/font> }<\/strong><\/font> }<\/strong><\/font> <\/pre>\n<\/p>\n
 Thanks to Christopher Zimmermann for the patch to kill children recursively. <\/p>\n","protected":false},"excerpt":{"rendered":"
I’ve released randomplay 0.48. randomplay is my command-line ‘itch a scratch’ music player. It is most useful for maintaining a random shuffle over many sessions—for example, I use it to make sure I don’t ever hear the same song in any three month period. The new version fixes a bug that prevented randomplay from advancing […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[17],"tags":[],"_links":{"self":[{"href":"http:\/\/adam.rosi-kessel.org\/weblog\/wp-json\/wp\/v2\/posts\/125"}],"collection":[{"href":"http:\/\/adam.rosi-kessel.org\/weblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/adam.rosi-kessel.org\/weblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/adam.rosi-kessel.org\/weblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/adam.rosi-kessel.org\/weblog\/wp-json\/wp\/v2\/comments?post=125"}],"version-history":[{"count":0,"href":"http:\/\/adam.rosi-kessel.org\/weblog\/wp-json\/wp\/v2\/posts\/125\/revisions"}],"wp:attachment":[{"href":"http:\/\/adam.rosi-kessel.org\/weblog\/wp-json\/wp\/v2\/media?parent=125"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/adam.rosi-kessel.org\/weblog\/wp-json\/wp\/v2\/categories?post=125"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/adam.rosi-kessel.org\/weblog\/wp-json\/wp\/v2\/tags?post=125"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}