### recsel -p example

Source: https://www.gnu.org/software/recutils/manual/html_node/Invoking-recsel.html

Example of using the -p option to print specific fields (Name and Email) for each matching record.

```text
-p Name,Email

```

--------------------------------

### Example recfile stock.rec

Source: https://www.gnu.org/software/recutils/manual/html_node/Deleting-Records.html

A sample recfile with three records, each having Title and Expiry fields. Used as the input for the recdel example.

```recfile
%rec: Item
%type: Expiry date
%sort: Title

Title: First Aid Kit
Expiry: 2 May 2009

Title: Emergency Rations
Expiry: 10 August 2009

Title: Life raft
Expiry: 2 March 2009

```

--------------------------------

### recset number option example

Source: https://www.gnu.org/software/recutils/manual/html_node/Invoking-recset.html

Example of using the -n option to specify record positions.

```bash
-n 0,2,4-9
```

--------------------------------

### Exact size constraint example

Source: https://www.gnu.org/software/recutils/manual/html_node/Size-Constraints.html

Example of a record descriptor using %size to require exactly 7 records of type Day.

```rec
%rec: Day
%size: 7
%type: Name enum
+ Monday Tuesday Wednesday Thursday Friday
+ Saturday Sunday
%doc: There should be exactly 7 days.

```

--------------------------------

### Relational size constraint example

Source: https://www.gnu.org/software/recutils/manual/html_node/Size-Constraints.html

Example using the <= operator to limit the number of Item records to at most 100.

```rec
%rec: Item
%key: Id
%size: <= 100
%doc: We have at most 100 different articles.

```

--------------------------------

### Example recfile with multiple record types

Source: https://www.gnu.org/software/recutils/manual/html_node/Selecting-by-Type.html

A sample recfile named gnu.rec containing two record types: Maintainer and Package. This file is used in the subsequent recsel examples.

```rec
%rec: Maintainer

Name: Jose E. Marchesi
Email: jemarch@gnu.org

Name: Luca Saiu 
Email: positron@gnu.org

%rec: Package

Name: GNU recutils
LastRelease: 12 February 2014

Name: GNU epsilon
LastRelease: 10 March 2013

```

--------------------------------

### Example database marks.rec

Source: https://www.gnu.org/software/recutils/manual/html_node/Adding-Anonymous-Records.html

A sample recfile containing records of type Marks.

```text
%rec: Marks
%type: Class enum A B C

Name: Alfred
Class: A

Name: Bertram
Class: B


```

--------------------------------

### Enforce date order with %constraint

Source: https://www.gnu.org/software/recutils/manual/html_node/Arbitrary-Constraints.html

Example of a Task record type where the Start date must occur before the End date.

```recutils
%rec: Task
%type: Start,End date
%constraint: Start << End
```

--------------------------------

### Example recfile with Date of Birth

Source: https://www.gnu.org/software/recutils/manual/html_node/Selecting-by-predicate.html

A sample recfile structure using a date type for the Dob field.

```text
# Date of Birth
%type: Dob date

Name: Alfred Nebel
Dob: 20 April 2010
Email: alf@example.com

Name: Bertram Worcester
Dob: 3 January 1966
Email: bert@example.com

Name: Charles Spencer
Dob: 4 July 1997
Email: charlie@example.com

Name: Dirk Hogart
Dob: 29 June 1945
Email: dirk@example.com

Name: Ernest Wright
Dob: 26 April 1978
Email: ernie@example.com
```

--------------------------------

### Using comments for headers and markers

Source: https://www.gnu.org/software/recutils/manual/html_node/Comments.html

Example demonstrating the use of comments for file headers, TODO lists, and section markers.

```rec
# -*- mode: rec -*-
#
# TODO
#
# This file contains the Bugs database of GNU recutils.
#
# Blah blah...

...

# End of TODO

```

--------------------------------

### Example record with multiple Email fields

Source: https://www.gnu.org/software/recutils/manual/html_node/Field-Expressions.html

A sample record used to demonstrate field selection with subscripts.

```text
Name: Mr. Foo
Email: foo@foo.com
Email: foo@foo.org
Email: mr.foo@foo.org
```

--------------------------------

### Example of a malformed recfile

Source: https://www.gnu.org/software/recutils/manual/html_node/Syntactical-Errors.html

A recfile example containing a syntactical error where the colon is missing after the field name.

```text
%rec: Article
%key  Id

Name: Thing
Id:   0

```

--------------------------------

### Using pipes to include record descriptors

Source: https://www.gnu.org/software/recutils/manual/html_node/Remote-Descriptors.html

A command-line example showing how to combine a descriptor file and a data file using pipes.

```bash
$ cat descriptor.rec data.rec | recsel ...
```

--------------------------------

### Get help for readrec built-in

Source: https://www.gnu.org/software/recutils/manual/html_node/Bash-Builtins.html

Use the bash help command to display help for the readrec built-in.

```bash
$ help readrec

```

--------------------------------

### Example Item record without auto-generated fields

Source: https://www.gnu.org/software/recutils/manual/html_node/Auto_002dGenerated-Fields.html

A sample recfile record structure using Description as the key.

```rec
%rec: Item
%key: Description

Description: 2cm metal soldier WWII
Amount: 2111

Description: Flying Helicopter Indoor Maxi
Amount: 8

...
```

--------------------------------

### %mandatory example with address book

Source: https://www.gnu.org/software/recutils/manual/html_node/Mandatory-Fields.html

Example of using %mandatory to require a Name field in every Contact record. The records shown include Name and other optional fields.

```rec
%rec: Contact
%mandatory: Name

Name: Granny
Phone: +12 23456677

Name: Yoyodyne Corp.
Email: sales@yoyod.com
Phone: +98 43434433

```

--------------------------------

### Record with multiple Email fields for alias example

Source: https://www.gnu.org/software/recutils/manual/html_node/Field-Expressions.html

Sample record used to demonstrate aliases with different positions.

```text
Name: Mr. Foo
Email: primary@email.com
Email: secondary@email.com
Email: other@email.com
```

--------------------------------

### String Literals

Source: https://www.gnu.org/software/recutils/manual/html_node/SEX-Operands.html

Examples of string literals delimited by single or double quotes.

```text
'Hello.'
'The following example is the empty string.'
''
```

--------------------------------

### recinf default output

Source: https://www.gnu.org/software/recutils/manual/html_node/Invoking-recinf.html

Example output showing the record type name and count for multiple input files.

```bash
$ recinf hackers.rec tasks.rec
25 Hacker
102 Task
```

--------------------------------

### Commenting out registers and fields

Source: https://www.gnu.org/software/recutils/manual/html_node/Comments.html

Example showing how to comment out specific fields or data within a recfile record.

```rec
Name: Jose E. Marchesi
# Occupation: Software Engineer
# Severe lack of brain capacity
# Fired on 02/01/2009 (without compensation)
Occupation: Unoccupied

```

--------------------------------

### Event database with integer IDs

Source: https://www.gnu.org/software/recutils/manual/html_node/Unique-Identifiers.html

Example of an Event database using simple integer-based auto-generated IDs.

```rec
%rec: Event
%key: Id
%mandatory: Title Date

Id: 0
Title: Team meeting
Date: 12-08-2013

Id: 1
Title: Dave's birthday
Date: 20-12-2013
```

--------------------------------

### Account database record structure

Source: https://www.gnu.org/software/recutils/manual/html_node/Decrypting-Data.html

Example of a recutils database file with a confidential Password field.

```rec
%rec: Account
%key: Login
%confidential: Password

Login: foo
Name: Mr. Foo
Email: foo@foo.com
Password: encrypted-AAABBBCCCDDD

Login: bar
Name: Ms. Bar
Email: bar@bar.org
Password: encrypted-XXXYYYZZZUUU

```

--------------------------------

### Defining Record Sets with %rec and %doc Fields

Source: https://www.gnu.org/software/recutils/manual/html_node/Documenting-Records.html

Example showing two record sets, 'Contact' and 'Associate', each defined with a %rec name and a descriptive %doc field.

```rec
%rec: Contact
%doc: Family, friends and acquaintances (other than business).

Name: Granny
Phone: +12 23456677

Name: Edwina
Phone: +55 0923 8765


%rec: Associate
%doc: Colleagues and other business contacts

Name: Karl Schmidt
Phone: +49 88234566

Name: Genevieve Curie
Phone: +33 34 87 65
```

--------------------------------

### date command examples for relative month calculation

Source: https://www.gnu.org/software/recutils/manual/html_node/Relative-items-in-date-strings.html

Shows how 'date -R' and 'date --date' handle relative month calculations. The example '2020-07-31 -1 month' may evaluate to July 1 due to invalid June 31, so using the 15th of the month gives the correct previous month.

```shell
$ date -R
Thu, 31 Jul 2020 13:02:39 -0400
$ date --date='-1 month' +'Last month was %B?'
Last month was July?
$ date --date="$(date +%Y-%m-15) -1 month" +'Last month was %B!'
Last month was June!
```

--------------------------------

### Sample contacts database

Source: https://www.gnu.org/software/recutils/manual/html_node/readrec.html

A simple recutils database with contacts, including multiple Email fields and a Checked field. Used as input for the readrec example.

```rec
Name: Mr. Foo
Email: foo@bar.com
Email: bar@baz.net
Checked: no

Name: Mr. Bar
Email: bar@foo.com
Telephone: 999666000
Checked: yes

```

--------------------------------

### Example org-mode results table

Source: https://www.gnu.org/software/recutils/manual/html_node/Using-ob_002drec_002eel.html

The output produced by the org-mode source block, displayed as an org table.

```org
#+RESULTS:
| Title               | Author          | Date            | Location |
|---------------------+-----------------+-----------------+----------|
| The Colour of Magic | Terry Pratchett | 4/20/01 11:15pm | loaned   |

```

--------------------------------

### Field Name References

Source: https://www.gnu.org/software/recutils/manual/html_node/SEX-Operands.html

Examples of using field names as operands in selection expressions.

```text
Name
Email
long_field_name
```

--------------------------------

### Define real fields with examples

Source: https://www.gnu.org/software/recutils/manual/html_node/Scalar-Field-Types.html

Defines a record with real fields Width and Height, showing valid real values including an integer-like value.

```rec
%rec: Rectangle
%typedef: Longitude_t real
%type: Width  Longitude_t
%type: Height Longitude_t

Width: 25.01
Height: 10

```

--------------------------------

### Example Item record with manual Id field

Source: https://www.gnu.org/software/recutils/manual/html_node/Auto_002dGenerated-Fields.html

A sample recfile record structure using a manual numeric Id as the primary key.

```rec
%rec: Item
%key: Id
%mandatory: Description

Id: 0
Description: 2cm metal soldier WWII
Amount: 2111

Id: 1
Description: Flying Helicopter Indoor Maxi
Amount: 8

...
```

--------------------------------

### Numeric Literals

Source: https://www.gnu.org/software/recutils/manual/html_node/SEX-Operands.html

Examples of integer and real number literals, including negative values and different base representations.

```text
10000
0
0xFF
-0xa
012
-07
-1342
.12
-3.14
```

--------------------------------

### Example database with %rec, %type, and %mandatory fields

Source: https://www.gnu.org/software/recutils/manual/html_node/Record-Sets-Properties.html

Shows a recutils database where the record descriptor specifies an optional numeric 'Id' field via %type and a mandatory 'Title' field via %mandatory. The %rec field names the record type 'Item'. Note that special fields always start with '%'.

```rec
%rec: Item
%type: Id int
%mandatory: Title

Id: 10
Title: Notebook (big)

Id: 11
Title: Fountain Pen

```

--------------------------------

### Sample Shop Inventory Database

Source: https://www.gnu.org/software/recutils/manual/html_node/Grouping-Records.html

A sample recfile containing shop inventory items with fields for Type, Category, Price, LastSell, and Available.

```text
Type: EC Car
Category: Toy
Price: 12.2
LastSell: 20-April-2012
Available: 623

Type: Terria
Category: Food
Price: 0.60
LastSell: 22-April-2012
Available: 8239

Type: Typex
Category: Office
Price: 1.20
LastSell: 22-April-2012
Available: 10878

Type: Notebook
Category: Office
Price: 1.00
LastSell: 21-April-2012
Available: 77455

Type: Sexy Puzzle
Category: Toy
Price: 6.20
LastSell: 6.20
Available: 12
```

--------------------------------

### Add the first record to a database with recins

Source: https://www.gnu.org/software/recutils/manual/html_node/Adding-Records-With-recins.html

Demonstrates adding a record with Name and Email fields to an empty contacts.rec file using -f and -v flags.

```bash
$ recins -f Name -v "Mr Foo" -f Email -v foo@bar.baz contacts.rec
$ cat contacts.rec
Name: Mr. Foo
Email: foo@bar.baz

```

--------------------------------

### Invalid inline comment example

Source: https://www.gnu.org/software/recutils/manual/html_node/Comments.html

Example showing that the '#' character does not initiate a comment when placed in the middle of a line.

```rec
Name: Peter the Great # Russian Tsar
Age: 53   

```

--------------------------------

### Examples of regexp field values

Source: https://www.gnu.org/software/recutils/manual/html_node/String-Field-Types.html

Shows valid and invalid values for a field of type `Id_t`. The first example matches the pattern; the second does not.

```rec
IDCard: 123456789Z
IDCard: invalid id card

```

--------------------------------

### Examples of line field values

Source: https://www.gnu.org/software/recutils/manual/html_node/String-Field-Types.html

Shows valid and invalid values for a field of type `line`. The third example is invalid because it contains a newline.

```rec
Name: Mr. Foo Bar
Name: Mrs. Bar Baz
Name: This is
+ invalid

```

--------------------------------

### Relative date item examples

Source: https://www.gnu.org/software/recutils/manual/html_node/Relative-items-in-date-strings.html

Examples of relative date items that adjust the current date forward or backward. Effects accumulate, and units include year, month, day, etc.

```text
1 year
1 year ago
3 years
2 days
```

--------------------------------

### Boolean field literals

Source: https://www.gnu.org/software/recutils/manual/html_node/Enumerated-Field-Types.html

Examples of valid literals for boolean fields.

```recutils
SwitchedOn: 1
SwitchedOn: yes
SwitchedOn: false
```

--------------------------------

### Alias example

Source: https://www.gnu.org/software/recutils/manual/html_node/Field-Expressions.html

Field expression that renames the Email field to ElectronicMail.

```text
Name,Email:ElectronicMail
```

--------------------------------

### recdel synopsis

Source: https://www.gnu.org/software/recutils/manual/html_node/Invoking-recdel.html

Shows the command-line syntax for recdel, including options for type, indexes, expression, quick, and random. If no file is given, recdel acts as a filter reading from standard input and writing to standard output.

```bash
recdel [OPTIONS]... [-t type] \
       [-n indexes | -e record_expr | -q str | -m num] \
       [file]

```

--------------------------------

### Escaped String Literals

Source: https://www.gnu.org/software/recutils/manual/html_node/SEX-Operands.html

Examples of strings containing escaped delimiter characters.

```text
'This string contains an apostrophe: \'.' 
"This one a double quote: \" ."
```

--------------------------------

### Example of type aliasing

Source: https://www.gnu.org/software/recutils/manual/html_node/Declaring-Types.html

Defining multiple types as aliases for an integer type.

```text
%typedef: Id_t          int
%typedef: Item_t        Id_t
%typedef: Transaction_t Id_t
```

--------------------------------

### Record descriptor with %sort and sample data

Source: https://www.gnu.org/software/recutils/manual/html_node/Sorted-Output.html

Example of a record descriptor using %sort to order inventory records by date. The database is not physically ordered; unsorted record sets are not a data integrity problem.

```recfile
%rec: Item
%type: Date date
%sort: Date

Id: 1
Title: Staplers
Date: 10 February 2011

Id: 2
Title: Ruler Pack 20
Date: 2 March 2009

...

```

--------------------------------

### List all tables including system tables

Source: https://www.gnu.org/software/recutils/manual/html_node/Importing-MDB-Files.html

Use the -s and -l options to include system tables (prefixed with MSys) in the listing.

```bash
$ mdb2rec -s -l sales.mdb
MSysObjects
MSysACEs
MSysQueries
MSysRelationships
Customers
Products
Orders
```

--------------------------------

### Select multiple fields with combined predicates

Source: https://www.gnu.org/software/recutils/manual/html_node/Selecting-by-predicate.html

Demonstrates using multiple -e arguments with logical AND (&&) and selecting multiple fields with -p.

```bash
$ recfix acquaintances.rec
$ recsel -e "Dob >> '31 July 1994' && Dob << '01 August 1998'" \
  -p Name,Email acquaintances.rec
Name: Charles Spencer
Email: charlie@example.com
```

--------------------------------

### Define enumerated types

Source: https://www.gnu.org/software/recutils/manual/html_node/Enumerated-Field-Types.html

Examples of defining enumerated types using the %typedef directive.

```recutils
%typedef: Status_t enum NEW STARTED DONE CLOSED
%typedef: Day_t enum Monday Tuesday Wednesday Thursday Friday
+                    Saturday Sunday
```

--------------------------------

### Invalid circular type definition

Source: https://www.gnu.org/software/recutils/manual/html_node/Declaring-Types.html

An example of an invalid set of declarations that creates a loop.

```text
%typedef: A_t B_t
%typedef: B_t C_t
%typedef: C_t A_t
```

--------------------------------

### recinf synopsis

Source: https://www.gnu.org/software/recutils/manual/html_node/Invoking-recinf.html

The basic command structure for invoking recinf.

```bash
recinf [option]... [file]...
```

--------------------------------

### Example of a record descriptor

Source: https://www.gnu.org/software/recutils/manual/html_node/Remote-Descriptors.html

A record set containing transactions with the type Transaction defined in the descriptor.

```text
%rec: Transaction

Id: 10
Title: House rent

Id: 11
Title: Loan
```

--------------------------------

### Grouping by Category with recsel

Source: https://www.gnu.org/software/recutils/manual/html_node/Grouping-Records.html

Example of using the -G argument to group records by the Category field.

```bash
$ recsel -G Category
Type: Terria
Category: Food
Price: 0.60
LastSell: 22-April-2012
Available: 8239

Type: Typex
Category: Office
Price: 1.20
LastSell: 22-April-2012
Available: 10878
Type: Notebook
Price: 1.00
LastSell: 21-April-2012
Available: 77455

Type: EC Car
Category: Toy
Price: 12.2
LastSell: 20-April-2012
Available: 623
Type: Sexy Puzzle
Price: 6.20
LastSell: 6.20
Available: 12
```

--------------------------------

### recfmt synopsis

Source: https://www.gnu.org/software/recutils/manual/html_node/Invoking-recfmt.html

The basic command-line syntax for invoking the recfmt utility.

```bash
recfmt [option]... [template]
```

--------------------------------

### Add a second record to a database with recins

Source: https://www.gnu.org/software/recutils/manual/html_node/Adding-Records-With-recins.html

Shows how subsequent invocations of recins append new records to the existing database file.

```bash
$ recins -f Name -v "Mr Bar" -f Email -v bar@gnu.org contacts.rec
$ cat contacts.rec
Name: Mr. Foo
Email: foo@bar.baz

name: Mr. Bar
Email: bar@gnu.org

```

--------------------------------

### Define enumerated types with comments

Source: https://www.gnu.org/software/recutils/manual/html_node/Enumerated-Field-Types.html

Example of defining an enumerated type with comments delimited by parentheses.

```recutils
%typedef: TaskStatus_t enum
+ NEW         (The task was just created)
+ IN_PROGRESS (Task started)
+ CLOSED      (Task closed)
```

--------------------------------

### Detailed aggregate with grouping

Source: https://www.gnu.org/software/recutils/manual/html_node/Aggregate-Functions.html

Display individual prices alongside the category average using grouping.

```bash
$ recsel -p "Category,Price,Avg(Price)" -G Category items.rec
Category: Food
Price: 0.60
Avg_Price: 0.600000

Category: Office
Price: 1.20
Price: 1.00
Avg_Price: 1.100000

Category: Toy
Price: 12.2
Price: 6.20
Avg_Price: 9.200000
```

--------------------------------

### recset synopsis

Source: https://www.gnu.org/software/recutils/manual/html_node/Invoking-recset.html

The basic command structure for invoking recset.

```bash
recset [option]... [file]...
```

--------------------------------

### recfix synopsis

Source: https://www.gnu.org/software/recutils/manual/html_node/Invoking-recfix.html

Shows the command-line synopsis for recfix. If no file is specified, recfix acts as a filter, reading from standard input and writing to standard output.

```text
recfix [option]... [operation] [op_option]... [file]

```