-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 What exactly is the limit on the length of a shebang line in an executable script, when called from within bash?
Most of what I read seems to indicate that it should be either 127 characters or kernel-dependent (and probably still 127 characters), but a few things seem to indicate that it might be 80 characters instead. I have a script whose shebang line, including the #! at the beginning, comes to exactly 129 characters. This is above both limits; attempting to run the script fails. If I move the executable targeted by the script to a different location and modify the shebang line appropriately (doable for testing purposes but not really practical for regular use - this is from a build system), it is now only 85 characters. This is above the 80-character limit but below the 127-character one; attempting to run the script succeeds. At a glance, that would seem to indicate that the 127-character limit is what applies. However, in the 129-character test case, the exact failure message prints only the first 79 characters of the shebang line, followed by "bad interpreter: No such file or directory". That would seem to indicate that it is trying to look for the path which it printed, which naturally is truncated and so does not exist. Thus, the error message I get with a 127-character path and 129-character shebang seems to indicate a 79- or 80-character shebang length limit, but the fact that the script succeeds with an 83-character path and 85-character shebang seems to indicate an at-least-85-character shebang length limit. This is somewhat confusing. What is the actual length limit, and what is the cause of this confusion? My best hypothesis so far is that the actual length limit is 127 characters, but that when printing the 'bad interpreter' error, bash truncates the printed shebang line to 80 (or 79) characters. That would explain the observed behaviors, but such a mismatch would seem unnecessarily confusing and misleading, since it A: gives a "No such file or directory" message for a path that (in this scenario) nothing ever actually tried to access, and B: indicates a lower apparent limit than what actually exists. If that isn't what's going on, then I'm stumped for the moment. - -- The Wanderer Secrecy is the beginning of tyranny. A government exists to serve its citizens, not to control them. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBCgAGBQJUCagEAAoJEASpNY00KDJrp+cP/2VMR/lNVMVyFCznAY5Q4NM8 F7ZykrlMvm8ZdLPdOnBEkYzKpikPue+WxiFWBr3LfOrB9QMJdkZb5tfAVa/Qwe4j adqKkJcBn6sj4JweJXPDO7Wju7/AcvGaNwIke5aM6LPrthIFdObpqemvxRMigwfE Q9u15OpaxwHmLJ6wrx++Wi6VbxuG0K0ctWTV4JQloadPizHwIF6yWSLZxTn7MpJp GWregvxyJ/tQey8NLPPGd6lg1riloFO2TcLX4b5yaAsl5Hzlw58k5fuFU/kdQYeC eHEeAZ1jPLMFDZgpfZettw2PvcSflPVvEsA291Lis44nBi83qe/ehv5ReoVYGRzE v1p14tgn2HWo3N8Xwl8QnHJ7+OF94jUJDZ6svK3XX+STwRpGx2gwGBNrNyhphAla /Yu0fE8wQCOt3nCorBT4c9OslfYgn45h2dWhjsKHfWOczHw3koXoRoIGiomPcrSW ps5VMR1JVEcTBoMQLIlbjoxHz6OnpCv9Q7pglMKlkn7mAybDNjVE8uXxgYw5cg4C Jl+gemCTeseVGZfsNwjwEwoBrlqPU3aWtB+HQ9DjXrjCyrE/+2iADgsGeOt/DxAg ANECb1ZGqhKrkxZs/Ft4Q5EWAlaMB7Ktg8S85CuMnRWYCYLkFdWhfIHemeH9TMEN QeTPv37KcaoBkkDYGMp3 =1iH6 -----END PGP SIGNATURE-----
