res = cur.execute("SELECT name FROM sqlite_master")
print(res.fetchone())
# ('movie',)
insert ข้อมูล
cur.execute("""
INSERT INTO movie VALUES
('Monty Python and the Holy Grail', 1975, 8.2),
('And Now for Something Completely Different', 1971, 7.5)
""")
con.commit()
select ข้อมูล
res = cur.execute("SELECT score FROM movie")
print(res.fetchall())
insert ข้อมูลด้วย executemany()
data = [
("Monty Python Live at the Hollywood Bowl", 1982, 7.9),
("Monty Python's The Meaning of Life", 1983, 7.5),
("Monty Python's Life of Brian", 1979, 8.0),
]
cur.executemany("INSERT INTO movie VALUES(?, ?, ?)", data)
con.commit() # Remember to commit the transaction after executing INSERT.
for row in cur.execute("SELECT year, title FROM movie ORDER BY year"):
print(row)
Verify that the database has been written to disk by calling con.close() to close the existing connection
BlazorServerApp6.Pages.Counter: Information: This is an INFORMATION message.
BlazorServerApp6.Pages.Counter: Warning: This is a WARNING message.
BlazorServerApp6.Pages.Counter: Error: This is an ERROR message.
using BlazorServerApp6.Data;
using Microsoft.AspNetCore.Components;
using Microsoft.AspNetCore.Components.Web;
var builder = WebApplication.CreateBuilder(args);
ILoggerFactory _loggerFactory = (ILoggerFactory)new LoggerFactory();
_loggerFactory.AddLog4Net();
builder.Services.AddSingleton(_loggerFactory);
// Add services to the container.
builder.Services.AddRazorPages();
builder.Services.AddServerSideBlazor();
builder.Services.AddSingleton<WeatherForecastService>();
var app = builder.Build();
// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
app.UseExceptionHandler("/Error");
// The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseRouting();
app.MapBlazorHub();
app.MapFallbackToPage("/_Host");
app.Run();
using Microsoft.AspNetCore.Mvc;
using System.Diagnostics;
using WebMvc6.Models;
namespace WebMvc6.Controllers
{
public class HomeController : Controller
{
private readonly ILogger<HomeController> _logger;
public HomeController(ILogger<HomeController> logger)
{
_logger = logger;
}
public IActionResult Index()
{
_logger.LogInformation("This is an INFORMATION message.");
_logger.LogWarning("This is a WARNING message.");
_logger.LogError("This is an ERROR message.");
return View();
}
public IActionResult Privacy()
{
return View();
}
[ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true)]
public IActionResult Error()
{
return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });
}
}
}
เปิดหน้าต่าง Output โดยไปที่เมนู View | Output
ทดลองเรียกไปที่หน้า Home เช่น https://localhost:7138/ แล้วดูที่หน้าต่าง Output
WebMvc6.Controllers.HomeController: Information: This is an INFORMATION message.
WebMvc6.Controllers.HomeController: Warning: This is a WARNING message.
WebMvc6.Controllers.HomeController: Error: This is an ERROR message.
var builder = WebApplication.CreateBuilder(args);
ILoggerFactory _loggerFactory = (ILoggerFactory)new LoggerFactory();
_loggerFactory.AddLog4Net();
builder.Services.AddSingleton(_loggerFactory);
// Add services to the container.
builder.Services.AddControllersWithViews();
var app = builder.Build();
// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
app.UseExceptionHandler("/Home/Error");
// The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseRouting();
app.UseAuthorization();
app.MapControllerRoute(
name: "default",
pattern: "{controller=Home}/{action=Index}/{id?}");
app.Run();
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
namespace WebApp6.Pages
{
public class IndexModel : PageModel
{
private readonly ILogger<IndexModel> _logger;
public IndexModel(ILogger<IndexModel> logger)
{
_logger = logger;
}
public void OnGet()
{
_logger.LogInformation("This is an INFORMATION message.");
_logger.LogWarning("This is a WARNING message.");
_logger.LogError("This is an ERROR message.");
}
}
}
เปิดหน้าต่าง Output โดยไปที่เมนู View | Output
ทดลองเรียกไปที่หน้า Home เช่น https://localhost:7138/ แล้วดูที่หน้าต่าง Output
WebApp6.Pages.IndexModel: Information: This is an INFORMATION message.
WebApp6.Pages.IndexModel: Warning: This is a WARNING message.
WebApp6.Pages.IndexModel: Error: This is an ERROR message.
var builder = WebApplication.CreateBuilder(args);
ILoggerFactory _loggerFactory = (ILoggerFactory)new LoggerFactory();
_loggerFactory.AddLog4Net();
builder.Services.AddSingleton(_loggerFactory);
// Add services to the container.
builder.Services.AddRazorPages();
var app = builder.Build();
// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
app.UseExceptionHandler("/Error");
// The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseRouting();
app.UseAuthorization();
app.MapRazorPages();
app.Run();
$ date --help
Usage: date [OPTION]... [+FORMAT]
or: date [-u|--utc|--universal] [MMDDhhmm[[CC]YY][.ss]]
Display the current time in the given FORMAT, or set the system date.
Mandatory arguments to long options are mandatory for short options too.
-d, --date=STRING display time described by STRING, not 'now'
-f, --file=DATEFILE like --date once for each line of DATEFILE
-I[TIMESPEC], --iso-8601[=TIMESPEC] output date/time in ISO 8601 format.
TIMESPEC='date' for date only (the default),
'hours', 'minutes', 'seconds', or 'ns' for date
and time to the indicated precision.
-r, --reference=FILE display the last modification time of FILE
-R, --rfc-2822 output date and time in RFC 2822 format.
Example: Mon, 07 Aug 2006 12:34:56 -0600
--rfc-3339=TIMESPEC output date and time in RFC 3339 format.
TIMESPEC='date', 'seconds', or 'ns' for
date and time to the indicated precision.
Date and time components are separated by
a single space: 2006-08-07 12:34:56-06:00
-s, --set=STRING set time described by STRING
-u, --utc, --universal print or set Coordinated Universal Time (UTC)
--help display this help and exit
--version output version information and exit
FORMAT controls the output. Interpreted sequences are:
%% a literal %
%a locale's abbreviated weekday name (e.g., Sun)
%A locale's full weekday name (e.g., Sunday)
%b locale's abbreviated month name (e.g., Jan)
%B locale's full month name (e.g., January)
%c locale's date and time (e.g., Thu Mar 3 23:05:25 2005)
%C century; like %Y, except omit last two digits (e.g., 20)
%d day of month (e.g., 01)
%D date; same as %m/%d/%y
%e day of month, space padded; same as %_d
%F full date; same as %Y-%m-%d
%g last two digits of year of ISO week number (see %G)
%G year of ISO week number (see %V); normally useful only with %V
%h same as %b
%H hour (00..23)
%I hour (01..12)
%j day of year (001..366)
%k hour, space padded ( 0..23); same as %_H
%l hour, space padded ( 1..12); same as %_I
%m month (01..12)
%M minute (00..59)
%n a newline
%N nanoseconds (000000000..999999999)
%p locale's equivalent of either AM or PM; blank if not known
%P like %p, but lower case
%r locale's 12-hour clock time (e.g., 11:11:04 PM)
%R 24-hour hour and minute; same as %H:%M
%s seconds since 1970-01-01 00:00:00 UTC
%S second (00..60)
%t a tab
%T time; same as %H:%M:%S
%u day of week (1..7); 1 is Monday
%U week number of year, with Sunday as first day of week (00..53)
%V ISO week number, with Monday as first day of week (01..53)
%w day of week (0..6); 0 is Sunday
%W week number of year, with Monday as first day of week (00..53)
%x locale's date representation (e.g., 12/31/99)
%X locale's time representation (e.g., 23:13:48)
%y last two digits of year (00..99)
%Y year
%z +hhmm numeric time zone (e.g., -0400)
%:z +hh:mm numeric time zone (e.g., -04:00)
%::z +hh:mm:ss numeric time zone (e.g., -04:00:00)
%:::z numeric time zone with : to necessary precision (e.g., -04, +05:30)
%Z alphabetic time zone abbreviation (e.g., EDT)
By default, date pads numeric fields with zeroes.
The following optional flags may follow '%':
- (hyphen) do not pad the field
_ (underscore) pad with spaces
0 (zero) pad with zeros
^ use upper case if possible
# use opposite case if possible
After any flags comes an optional field width, as a decimal number;
then an optional modifier, which is either
E to use the locale's alternate representations if available, or
O to use the locale's alternate numeric symbols if available.
Examples:
Convert seconds since the epoch (1970-01-01 UTC) to a date
$ date --date='@2147483647'
Show the time on the west coast of the US (use tzselect(1) to find TZ)
$ TZ='America/Los_Angeles' date
Show the local time for 9AM next Friday on the west coast of the US
$ date --date='TZ="America/Los_Angeles" 09:00 next Fri'
GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
For complete documentation, run: info coreutils 'date invocation'
$ date --version
date (GNU coreutils) 8.22
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Written by David MacKenzie.
ตัวอย่าง
Open a terminal application and type the following command:
$ date
Tue Feb 7 15:23:13 +07 2023
format the date
$ date +"%y-%m-%d"
23-02-07
$ date +"%Y-%m-%d"
2023-02-07
Simply display the current time on Linux:
]$ date "+%T"
15:24:15
To print the date of the day before yesterday, run:
$ date --date='2 days ago'
Sun Feb 5 15:25:37 +07 2023
Want to see the day of year of Christmas in the current year? Try:
$ date --date='25 Dec' +%j
359
Display the current full month name and the day of the month:
It is easy to see the syntax of a function and believe you know how to use it. But it is always a better choice to understand a function through examples because they help you understand the role that different aspects of a function play.
Here are some useful examples of if-else in shell scripts to give you a better idea of how to use this tool.
Command
Description
&&
Logical AND
$0
Argument 0 i.e. the command that’s used to run the script
$1
First argument (change number to access further arguments)
-eq
Equality check
-ne
Inequality check
-lt
Less Than
-le
Less Than or Equal
-gt
Greater Than
-ge
Greater Than or Equal
1. Using if-else to check whether two numbers are equal
When trying to understand the working of a function like if-else in a shell script, it is good to start things simple. Here, we initialize two variables a and b, then use the if-else function to check if the two variables are equal. The bash script should look as follows for this task.
#!/bin/bash
m=1
n=2
if [ $n -eq $m ]
then
echo "Both variables are the same"
else
echo "Both variables are different"
fi
Output:
Both variables are different
2. Using if-else to compare two values
The more common use of if-else in shell scripts is for comparing two values. Comparing a variable against another variable or a fixed value helps is used in a variety of cases by all sorts of programmers.
For the sake of this example, we will be initializing two variables and using the if-else function to find the variable which is greater than the other.
#!/bin/bash
a=2
b=7
if [ $a -ge $b ]
then
echo "The variable 'a' is greater than the variable 'b'."
else
echo "The variable 'b' is greater than the variable 'a'."
fi
Output:
The variable 'b' is greater than the variable 'a'.
3. Using if-else to check whether a number is even
Sometimes we come across situations where we need to deal with and differentiate between even and odd numbers. This can be done with if-else in shell scripts if we take the help of the modulus operator.
The modulus operator divides a number with a divisor and returns the remainder.
As we know all even numbers are a multiple of 2, we can use the following shell script to check for us whether a number is even or odd.
#!/bin/bash
n=10
if [ $((n%2))==0 ]
then
echo "The number is even."
else
echo "The number is odd."
fi
Output:
The number is even
As you can see, we’ve enclosed a part of the condition within double brackets. That’s because we need the modulus operation to be performed before the condition is checked.
Also, enclosing in double brackets runs statements in C-style allowing you to process some C-style commands within bash scripts.
4. Using if-else as a simple password prompt
The if-else function is known for its versatility and range of application. In this example, we will use if-else in shell script to make the interface for a password prompt.
To do this, we will ask the user to enter the password and store it in the variable pass.
If it matches the pre-defined password, which is ‘password’ in this example, the user will get the output as -“The password is correct”.
Else, the shell script will tell the user that the password was incorrect and ask them to try again.
#!/bin/bash
echo "Enter password"
read pass
if [ $pass="password" ]
then
echo "The password is correct."
else
echo "The password is incorrect, try again."
fi
The pgrep command allows a user to find process IDs in the running program in the system’s current state.
$ pgrep --version
pgrep from procps-ng 3.3.10
$ pgrep --help
Usage:
pgrep [options] <pattern>
Options:
-d, --delimiter <string> specify output delimiter
-l, --list-name list PID and process name
-a, --list-full list PID and full command line
-v, --inverse negates the matching
-w, --lightweight list all TID
-c, --count count of matching processes
-f, --full use full process name to match
-g, --pgroup <PGID,...> match listed process group IDs
-G, --group <GID,...> match real group IDs
-n, --newest select most recently started
-o, --oldest select least recently started
-P, --parent <PPID,...> match only child processes of the given parent
-s, --session <SID,...> match session IDs
-t, --terminal <tty,...> match by controlling terminal
-u, --euid <ID,...> match by effective IDs
-U, --uid <ID,...> match by real IDs
-x, --exact match exactly with the command name
-F, --pidfile <file> read PIDs from file
-L, --logpidfile fail if PID file is not locked
--ns <PID> match the processes that belong to the same
namespace as <pid>
--nslist <ns,...> list which namespaces will be considered for
the --ns option.
Available namespaces: ipc, mnt, net, pid, user, uts
-h, --help display this help and exit
-V, --version output version information and exit
For more details see pgrep(1).