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Append a record to the end of a text file: Difference between revisions
Append a record to the end of a text file (view source)
Revision as of 14:18, 6 July 2019
, 4 years agoRust implementation
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</pre>
=={{header|Rust}}==
<lang rust>
use std::fs::File;
use std::fs::OpenOptions;
use std::io::BufRead;
use std::io::BufReader;
use std::io::BufWriter;
use std::io::Result;
use std::io::Write;
use std::path::Path;
/// Password record with all fields
#[derive(Eq, PartialEq, Debug)]
pub struct PasswordRecord {
pub account: String,
pub password: String,
pub uid: u64,
pub gid: u64,
pub gecos: Vec<String>,
pub directory: String,
pub shell: String,
}
impl PasswordRecord {
/// new instance, cloning all fields
pub fn new(
account: &str,
password: &str,
uid: u64,
gid: u64,
gecos: Vec<&str>,
directory: &str,
shell: &str,
) -> PasswordRecord {
PasswordRecord {
account: account.to_string(),
password: password.to_string(),
uid,
gid,
gecos: gecos.iter().map(|s| s.to_string()).collect(),
directory: directory.to_string(),
shell: shell.to_string(),
}
}
/// convert to one line string
pub fn to_line(&self) -> String {
let gecos = self.gecos.join(",");
format!(
"{}:{}:{}:{}:{}:{}:{}",
self.account, self.password, self.uid, self.gid, gecos, self.directory, self.shell
)
}
/// read record from line
pub fn from_line(line: &str) -> PasswordRecord {
let sp: Vec<&str> = line.split(":").collect();
if sp.len() < 7 {
panic!("Less than 7 fields found");
} else {
let uid = sp[2].parse().expect("Cannot parse uid");
let gid = sp[3].parse().expect("Cannot parse gid");
let gecos = sp[4].split(",").collect();
PasswordRecord::new(sp[0], sp[1], uid, gid, gecos, sp[5], sp[6])
}
}
}
/// read all records from file
pub fn read_password_file(file_name: &str) -> Result<Vec<PasswordRecord>> {
let p = Path::new(file_name);
if !p.exists() {
Ok(vec![])
} else {
let f = OpenOptions::new().read(true).open(p)?;
Ok(BufReader::new(&f)
.lines()
.map(|l| PasswordRecord::from_line(&l.unwrap()))
.collect())
}
}
/// overwrite file with records
pub fn overwrite_password_file(file_name: &str, recs: &Vec<PasswordRecord>) -> Result<()> {
let f = OpenOptions::new()
.create(true)
.write(true)
.open(file_name)?;
write_records(f, recs)
}
/// append records to file
pub fn append_password_file(file_name: &str, recs: &Vec<PasswordRecord>) -> Result<()> {
let f = OpenOptions::new()
.create(true)
.append(true)
.open(file_name)?;
write_records(f, recs)
}
/// internal, write records line by line
fn write_records(f: File, recs: &Vec<PasswordRecord>) -> Result<()> {
let mut writer = BufWriter::new(f);
for rec in recs {
write!(writer, "{}\n", rec.to_line())?;
}
Ok(())
}
fn main(){
let recs1 = vec![
PasswordRecord::new(
"jsmith",
"x",
1001,
1000,
vec![
"Joe Smith",
"Room 1007",
"(234)555-8917",
"(234)555-0077",
"jsmith@rosettacode.org",
],
"/home/jsmith",
"/bin/bash",
),
PasswordRecord::new(
"jdoe",
"x",
1002,
1000,
vec![
"Jane Doe",
"Room 1004",
"(234)555-8914",
"(234)555-0044",
"jdoe@rosettacode.org",
],
"/home/jdoe",
"/bin/bash",
),
];
overwrite_password_file("passwd", &recs1).expect("cannot write file");
let recs2 = read_password_file("passwd").expect("cannot read file");
println!("Original file:");
for r in recs2 {
println!("{}",r.to_line());
}
let append0 = vec![PasswordRecord::new(
"xyz",
"x",
1003,
1000,
vec![
"X Yz",
"Room 1003",
"(234)555-8913",
"(234)555-0033",
"xyz@rosettacode.org",
],
"/home/xyz",
"/bin/bash",
)];
append_password_file("passwd", &append0).expect("cannot append to file");
let recs2 = read_password_file("passwd").expect("cannot read file");
println!("");
println!("Appended file:");
for r in recs2 {
println!("{}",r.to_line());
}
}
</lang>
{{out}}
<pre>
Original file:
jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash
jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash
Appended file:
jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash
jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash
xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
</pre>
=={{header|Scala}}==
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