May 2009 - Darwin-dev - lists.apple.com

Re: Setting st_flags returned by stat
by Terry Lambert 03 May '09

03 May '09

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com -- Terry Thanks. so I have to believe you are looking at your 10.4 system again. 2. If I do an lstat() on a file and take its st_flags: lstat(path, &statbuf); Is this right? -- Terry How do we set these flags back to a file? Should it be done using the chflags() function call? As Terry Lambert noted, you use the chflags() call to set flags on a file. However do not set undefined bits - only use the bits in /usr/include/sys/stat.h. Specifically these are: and if you're the super-user you can set: Keep in mind that most of these bits have defined meanings in the file system: IMMUTABLE and APPEND in particular. Bits such as NODUMP are not really used on MacOS X. --dominic _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… The reason you can't look at the link itself is that there are no APIs that internally set O_NOFOLLOW on the path lookup operations, and therefore what you end up with is the link target following the namei() call in the kernel to resolve the path -- it's resolving the target, not the link. Feel free to pass the same path to other functions which take path arguments, but you will be disappointed when, lacking the O_NOFOLLOW, they also resolve to the link target instead of the link. On May 1, 2009, at 11:51 PM, rohan a wrote: Atleast on my Mac 10.4 there does not seem to be any lchflags. I have only chflags() and fchflags() available to me. I will use getattrlist() and setattrlist() which provide ATTR_CMN_FLAGS to get/set the flags. On Sat, May 2, 2009 at 12:06 PM, rohan a <info1686(a)gmail.com> wrote: So doesn't Mac OS provide an API to work on symboic links rather than its target ? Something like an lstat(). On Sat, May 2, 2009 at 2:12 AM, Terry Lambert <tlambert(a)apple.com> wrote: On May 1, 2009, at 5:07 AM, rohan a wrote: Hello, Thanks for this. 1. However, man 2 stat says that st_flags is of type u_long, but chflags() takes as argument flags which is u_int. For 32 but systems, it doesn't matter. For 64 bit systems, it doesn't care because it's unsigned, so extension to long on LP64 won't change the values. On Leopard and later, it's defined as: /usr/include/sys/stat.h:int chflags(const char *, __uint32_t); and then use statbuf.st_flags in the chflags() call, to set the flags to another file: chflags(file, statbuf.st_flags); Careful; you are most likely operating on the link target, and not the symbolic link itself. It's only recently that you've been able to modify link attributes rather than link target attributes. Inferring tto much about symbolic links is a really bad idea, since it's FS dependent how they are implemented. What Might work in Leopard on HFS may not work in Tiger on HFS, and that may not be the same as some other filesystem (i.e. there were a number of filesystems that supported symbolic links as immediate files, meaning that all the attributes were inherited from the directory, since they only existed as a directory entry, and not as real files). Avoid writing code that assumes symbolic link semantics are the same between filesystem types. Yes, that means that if you back up on one system and restore on another, the symbolic links could act different, and in undesirable ways, unless you go out of your way to characterize behaviour on each FS type, and each version of an OS you might be archiving or dearchiving. This is why there are not 50,000 5 star backup/restore tools out there. On 5/1/09, Dominic Giampaolo <dbg(a)apple.com> wrote: The stat() / lstat() API returns st_flags which are "user defined flags for file". #define UF_NODUMP 0x00000001 /* do not dump file */ #define UF_IMMUTABLE 0x00000002 /* file may not be changed */ #define UF_APPEND 0x00000004 /* writes to file may only append */ #define UF_OPAQUE 0x00000008 /* directory is opaque wrt. union */ #define SF_ARCHIVED 0x00010000 /* file is archived */ #define SF_IMMUTABLE 0x00020000 /* file may not be changed */ #define SF_APPEND 0x00040000 /* writes to file may only append */ This email sent to site_archiver(a)lists.apple.com

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Re: Setting st_flags returned by stat
by Terry Lambert 02 May '09

02 May '09

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… This email sent to site_archiver(a)lists.apple.com

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Re: Setting st_flags returned by stat
by rohan a 02 May '09

02 May '09

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Re: Setting st_flags returned by stat
by rohan a 02 May '09

02 May '09

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:cc:content-type; bh=wZV1xV3J4uyNw9nCAGEir4HcYP0EOCQbO6G2lrC7s9g=; b=VQ7oETL8Ud2mrNJ9M2yset+MzJNl2GdGIDSKX6qGAIlIUYj2saWN2IdtiWc9c/wjcd DXAfrf1DTaqE+NQTzGnWVL/0Ee2QpG6G6PvnORR75zj2nL+6gnW85tqZ8WI0foySpavg XbEWO1QD6g83n8pcXQmcSLSfVtaOT8A7ROidA= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=i6HQHY8BLT8AfUyNPuimWV5R3Zem54wiMLKFxtWlA5QKIZCpUksxnFKh9CE8RJa1x1 328gahkU9xLzeLx+Wx6bMtYl3xT7Fep2frIl0c0xMjZmMj3l2z9qz9pHQY53+nH7gSUB sncPUuAiR9ETJB+0YxCqrVgF69bQW8fhYOzuA= _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… This email sent to site_archiver(a)lists.apple.com

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Re: Setting st_flags returned by stat
by rohan a 02 May '09

02 May '09

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:cc:content-type; bh=JyK3BhGOzcUstfHD1siFFspGxeTnxCkV1swhb0i2UcY=; b=T+8nPIQ1n25JS6xiCUBYh6mqzPfrJTNbWP7Di4JiaLsIYXJpWtntsvePhnWxA6wcf9 lyr8T0wTwlcPtTXRfU89fmMWEvOh7+CgEvAn3RsWEBFZmJP7KwKbeTGhX4ZJyMUTHQOC X4c6A5SaipCcAJey1vMbFofzWWpe1ybbw1SVo= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=HCMckzcxYnFcH08qaj1x4sdFy2ooiVEAtjaO99OC85Foikrp41iA5hXQRMkBeMAZDk tEgMjWeaPYMTbBlAN2bsLQZ+XyFViJRqjJJ+GXw9XzIxDc6sQhZhS0vimTL4pHM5t5UX h81wTq1F4r7MUSpEa6H5cPL8e1Lnv9JLGONhc= _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… This email sent to site_archiver(a)lists.apple.com

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Re: Setting st_flags returned by stat
by Terry Lambert 01 May '09

01 May '09

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com Hello, Thanks for this. /usr/include/sys/stat.h:int chflags(const char *, __uint32_t); so I have to believe you are looking at your 10.4 system again. 2. If I do an lstat() on a file and take its st_flags: lstat(path, &statbuf); -- Terry How do we set these flags back to a file? Should it be done using the chflags() function call? As Terry Lambert noted, you use the chflags() call to set flags on a file. However do not set undefined bits - only use the bits in /usr/include/sys/stat.h. Specifically these are: and if you're the super-user you can set: Keep in mind that most of these bits have defined meanings in the file system: IMMUTABLE and APPEND in particular. Bits such as NODUMP are not really used on MacOS X. --dominic _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… On May 1, 2009, at 5:07 AM, rohan a wrote: 1. However, man 2 stat says that st_flags is of type u_long, but chflags() takes as argument flags which is u_int. For 32 but systems, it doesn't matter. For 64 bit systems, it doesn't care because it's unsigned, so extension to long on LP64 won't change the values. On Leopard and later, it's defined as: and then use statbuf.st_flags in the chflags() call, to set the flags to another file: chflags(file, statbuf.st_flags); Is this right? Careful; you are most likely operating on the link target, and not the symbolic link itself. It's only recently that you've been able to modify link attributes rather than link target attributes. Inferring tto much about symbolic links is a really bad idea, since it's FS dependent how they are implemented. What Might work in Leopard on HFS may not work in Tiger on HFS, and that may not be the same as some other filesystem (i.e. there were a number of filesystems that supported symbolic links as immediate files, meaning that all the attributes were inherited from the directory, since they only existed as a directory entry, and not as real files). Avoid writing code that assumes symbolic link semantics are the same between filesystem types. Yes, that means that if you back up on one system and restore on another, the symbolic links could act different, and in undesirable ways, unless you go out of your way to characterize behaviour on each FS type, and each version of an OS you might be archiving or dearchiving. This is why there are not 50,000 5 star backup/restore tools out there. On 5/1/09, Dominic Giampaolo <dbg(a)apple.com> wrote: The stat() / lstat() API returns st_flags which are "user defined flags for file". #define UF_NODUMP 0x00000001 /* do not dump file */ #define UF_IMMUTABLE 0x00000002 /* file may not be changed */ #define UF_APPEND 0x00000004 /* writes to file may only append */ #define UF_OPAQUE 0x00000008 /* directory is opaque wrt. union */ #define SF_ARCHIVED 0x00010000 /* file is archived */ #define SF_IMMUTABLE 0x00020000 /* file may not be changed */ #define SF_APPEND 0x00040000 /* writes to file may only append */ This email sent to site_archiver(a)lists.apple.com

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Re: Setting st_flags returned by stat
by rohan a 01 May '09

01 May '09

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:cc:content-type; bh=w8g9ZvngFeiKp7tSfJv0G6dgzgBajKWeJGf+PmUh3X0=; b=Dl+6ZOR0+SGwr4GtbQAKZP2ZX35ISHDrEI5RK3n4aHzCoEJCUKPOaDPc/zNV7b4prR tSH7E928kZjqysUqPWca5qlQPAv06oYX6SrTSj0huI95QkMRxf/Cz0a6x+zRZGsn+SHG mHRmB0Nugy+k1hxy314mBBfPnxBk0T8Ft7ApI= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=jlvDSObibYSebCL70tscN4FhpKMa9J9IwJziHmRI/dQ8Dh4jnt/PYcJWx9U/RMLMuq YLZg7tRSzO4HpDsyoes48B0NflkWqFXl6JXz5JeGtYL7PSteMNt0Ux4T/qcsNHRS4t0s YQjifRskJ6xTlVMkkupHtRdljgSGvKmVF0HJY= _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… This email sent to site_archiver(a)lists.apple.com

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