unix

问题 I am trying to check a string for any Uppercase letter. my code shows NO UPPER for any input, may it be "sss", "Sss", "SSS" if [[ "$pass" =~ [^a-zA-Z0-9] ]] then echo "Upper found" else echo "no upper" fi 回答1: [^a-zA-Z0-9] means anything except for a-z , i.e. lowercase letters, A-Z , i.e. uppercase letters, and 0-9 , i.e. digits. sss , Sss , SSS all contain just letters, so they can't match. [[ $password =~ [A-Z] ]] is true if the password contains any uppercase letter. You should set LC_ALL

问题 What is the difference between sed -i -e and sed -ie ? It's not very clear from help sed --help -e script, --expression=script add the script to the commands to be executed In second case it creates some backup file? In general Unix utils do not permit to combine flags? Just an example to show what is happening: echo "bla" > 1.txt cat 1.txt bla sed -i -e 's:bla:blakva:g' 1.txt cat 1.txt blakva sed -ie 's:bla:blakva:g' 1.txt cat 1.txt blakvakva *Note: also 1.txte is created, containing cat 1

问题 I need to sort some data with unix sort but I can't figure exactly the right syntax, the data looks like 3.9.1 Step 10: 3.9.1 Step 20: 3.8.10 Step 20: 3.10.2 Step 10: 3.8.4 Step 90: 3.8.4 Step 100: 3.8.4 Step 10: I want to sort it using first the major number, then the step number, e.g. the data sorted above would look like. 3.8.4 Step 10: 3.8.4 Step 90: 3.8.4 Step 100: 3.8.10 Step 20: 3.9.1 Step 10: 3.9.1 Step 20: 3.10.2 Step 10: I have found the way to sort by first number on this site:

问题 I am reading 'UNIX Network Programming: The Sockets Networking API' and in the example code they have an error handling function which contains the following lines: fflush(stdout); /* in case stdout and stderr are the same */ fputs(buf, stderr); fflush(stderr); Where buf contains the error description. I don't understand why fflush is used on stdout on the first line and why the comment explains the reason for its use. 回答1: This is because of buffering. Stdout and stderr are usually buffered

问题 I have two git local repositories. Both share an identical file, under a different path and under a different name. Currently, when I make changes I have to copy the file from one directory to another. Is there an alternative way to keep them in sync without manually overwriting the file? I don't want to create a separate repository for this file. I thought one of the following things would work, but apparently, they don't: git submodule git subtree symlink soft symlink hard What else is

问题 I want to build a simple library with some undefined reference, as you can see in function_two.c , I call three() which is not defined. header.h void one(); void two(); void three(); function_one.c #include <stdio.h> #include "header.h" void one() { printf("one\n"); } function_two.c #include <stdio.h> #include "header.h" void two() { printf("two\n"); three(); } Using Linux , I compile both files and then I link them linux:~/example$ gcc -c -Wall -Werror -fpic function_one.c linux:~/example$

问题 I am new to Unix Programming. Could you please help me to solve the question. For example, If the input file has the below content RollNo Name Score 234 ABC 70 567 QWE 12 457 RTE 56 234 XYZ 80 456 ERT 45 The output will be ABC I tried something like this sort -k3,3 -rn -t" " | head -n2 | awk '{print $2}' 回答1: Using awk awk 'NR>1{arr[$3]=$2} END {n=asorti(arr,arr_sorted); print arr[arr_sorted[n-1]]}' Demo: $cat file.txt RollNo Name Score 234 ABC 70 567 QWE 12 457 RTE 56 234 XYZ 80 456 ERT 45

问题 Is there a command line I can issue to see what directory another user is currently working in? This would be like using >pwd but for the other user. 回答1: There's a cwd symlink in every process' /proc folder, but as a commoner you wouldn't have any rights to read any other's proc folder - only your own: [marc@panic home]$ ls -l /proc/$$/cwd lrwxrwxrwx. 1 marc marc 0 May 5 12:06 /proc/16257/cwd -> /home ^^^^^---cwd [marc@panic home]$ ^^^^---cwd 来源： https://stackoverflow.com/questions/23478833

问题 I'm trying to move my bot to an Ubuntu virtual server from Vultr but it's having a problem connecting to the postgres database. I've tried editing the config from md5 to true, and host to local, etc. But those only give me different errors and also make it stop working on my original machine too. It's working perfectly fine on my Windows machine. Here is the error I'm facing: asyncpg.exceptions.InvalidAuthorizationSpecificationError: no pg_hba.conf entry for host "[local]", user "postgres",

问题 I am writing a program on a hotel reservation system and have declared a struct Room as follows: struct Room { bool isavailable; bool ispaid; string customer; string date; }; I use a variable read from an input file to create an array of n structs which is all the rooms in the hotel. struct Room* rooms = new Room[numOfRooms]; I then create the shared memory space and attach it, but when I try to access it after, it doesn't seem to work. //creates shared memory space if((shmid = shmget(shmkey,