unix

问题 Say I have this file. $ cat a.txt c 1002 4 f 1001 1 d 1003 1 a 1001 3 e 1004 2 b 1001 2 I want to sort it by the second column and then by the third column. Column two are numbers, while column 3 can be treated as string. I know the following command works well. $ sort -k2,2n -k3,3 a.txt f 1001 1 b 1001 2 a 1001 3 c 1002 4 d 1003 1 e 1004 2 However, I think sort -k2n a.txt should also work, while it does not. $ sort -k2n a.txt a 1001 3 b 1001 2 f 1001 1 c 1002 4 d 1003 1 e 1004 2 Seems like

问题 Say I have this file. $ cat a.txt c 1002 4 f 1001 1 d 1003 1 a 1001 3 e 1004 2 b 1001 2 I want to sort it by the second column and then by the third column. Column two are numbers, while column 3 can be treated as string. I know the following command works well. $ sort -k2,2n -k3,3 a.txt f 1001 1 b 1001 2 a 1001 3 c 1002 4 d 1003 1 e 1004 2 However, I think sort -k2n a.txt should also work, while it does not. $ sort -k2n a.txt a 1001 3 b 1001 2 f 1001 1 c 1002 4 d 1003 1 e 1004 2 Seems like

问题 I have a shell script that starts unit tests for modules. I need the name of the module in all lowercase and with the first character uppercase. So far I have been doing it like this: #!/bin/sh -x # z.B. getbrowser strModuleToTest=$1 # g strModuleToTestUppercaseFirstletter=${strModuleToTest:0:1} # etbrowser strModuleToTestUppercaseLastletters=${strModuleToTest:1} # g -> G strModuleToTestUppercaseFirstletter="${strModuleToTestUppercaseFirstletter/a/A}" strModuleToTestUppercaseFirstletter="$

问题 I have a shell script that starts unit tests for modules. I need the name of the module in all lowercase and with the first character uppercase. So far I have been doing it like this: #!/bin/sh -x # z.B. getbrowser strModuleToTest=$1 # g strModuleToTestUppercaseFirstletter=${strModuleToTest:0:1} # etbrowser strModuleToTestUppercaseLastletters=${strModuleToTest:1} # g -> G strModuleToTestUppercaseFirstletter="${strModuleToTestUppercaseFirstletter/a/A}" strModuleToTestUppercaseFirstletter="$

问题 I've been looking for the equivalent python method for the unix cksum command: http://pubs.opengroup.org/onlinepubs/7990989775/xcu/cksum.html $ cksum ./temp.bin 1605138151 712368 ./temp.bin So far I have found the zlib.crc32() function >>> import zlib >>> f = open('./temp.bin','rb') >>> data = f.read() >>> zlib.crc32(data) 1128751837 However this code appears to produce different results. As far as I can tell this should be using the same crc polynomial but I imagine there must be some

问题 "uprintf() function outputs to the current process' controlling tty" This is description of uprintf() from Freebsd MAN. I don't understand what is tty? Thanks.Nice holiday! 回答1: A tty is an abstract model of a character I/O device. It is most directly a system interface, with corresponding application program interfaces. Once upon a time there was a corporation named Teletype . They made hardcopy automatic typewriter devices that were used as communications terminals for decades and then

问题 "uprintf() function outputs to the current process' controlling tty" This is description of uprintf() from Freebsd MAN. I don't understand what is tty? Thanks.Nice holiday! 回答1: A tty is an abstract model of a character I/O device. It is most directly a system interface, with corresponding application program interfaces. Once upon a time there was a corporation named Teletype . They made hardcopy automatic typewriter devices that were used as communications terminals for decades and then

问题 "uprintf() function outputs to the current process' controlling tty" This is description of uprintf() from Freebsd MAN. I don't understand what is tty? Thanks.Nice holiday! 回答1: A tty is an abstract model of a character I/O device. It is most directly a system interface, with corresponding application program interfaces. Once upon a time there was a corporation named Teletype . They made hardcopy automatic typewriter devices that were used as communications terminals for decades and then

问题 I was skimming through K&R C and I noticed that to read the entries in a directories, they used: while (read(dp->fd, (char *) &dirbuf, sizeof(dirbuf)) == sizeof(dirbuf)) /* code */ Where dirbuf was a system-specific directory structure, and dp->fd a valid file descriptor. On my system, dirbuf would have been a struct linux_dirent . Note that a struct linux_dirent has a flexible array member for the entry name, but let us assume, for the sake of simplicity, that it doesn't. (Dealing with the

问题 I was skimming through K&R C and I noticed that to read the entries in a directories, they used: while (read(dp->fd, (char *) &dirbuf, sizeof(dirbuf)) == sizeof(dirbuf)) /* code */ Where dirbuf was a system-specific directory structure, and dp->fd a valid file descriptor. On my system, dirbuf would have been a struct linux_dirent . Note that a struct linux_dirent has a flexible array member for the entry name, but let us assume, for the sake of simplicity, that it doesn't. (Dealing with the