grep 连带打印

要让 grep 在查询到匹配行时 连带打印它的上一行，可以使用 -B（Before）选项。具体命令如下：

grep -B 1 "prices_std_dev" /home/debian/tmp/logs/binance.log

说明：

• -B 1：显示匹配行 及之前的 1 行（-B 2 会显示前 2 行，依此类推）。
• 如果匹配行是文件的第一行，则不会打印不存在的“上一行”。

其他常用 grep 上下文控制选项：

例如：

# 显示匹配行及前后各 1 行
grep -C 1 "prices_std_dev" /home/debian/tmp/logs/binance.log

如果日志是结构化格式（如 JSON）

建议改用 jq 或 awk 更精准地提取上下文：

# 用 awk 打印匹配行及上一行
awk '/prices_std_dev/ {print prev_line; print $0} {prev_line=$0}' /home/debian/tmp/logs/binance.log

To let grep print the previous line when it finds a matching line, use the -B (Before) option. The specific command is as follows:

grep -B 1 "prices_std_dev" /home/debian/tmp/logs/binance.log

Description:

• -B 1: Display the matching line and the previous line (-B 2 will display the previous 2 lines, and so on).
• If the matching line is the first line of the file, the non-existent “previous line” will not be printed.

Other commonly used grep context control options:

before and after** (Context) |

For example:

# Display matching line and 1 line before and after
grep -C 1 "prices_std_dev" /home/debian/tmp/logs/binance.log

If the log is in a structured format (such as JSON),

it is recommended to use jq or awk to extract the context more accurately:

# Use awk to print the matching line and the previous line
awk '/prices_std_dev/ {print prev_line; print $0} {prev_line=$0}' /home/debian/tmp/logs/binance.log

如果你想要在 grep 匹配到目标行（如 "prices_std_dev"）后，再额外打印另一条件的行，可以通过以下方式实现：

方法 1：grep -A + 管道 + grep（推荐）

grep -A 1 "prices_std_dev" /home/debian/tmp/logs/binance.log | grep -A 1 "另一条件"

作用：

1. 先匹配 "prices_std_dev" 并输出该行及下一行（-A 1）。
2. 再对结果匹配 "另一条件"，输出符合条件的行及其下一行。

方法 2：awk（精确控制）

如果条件较复杂（例如需要匹配不同关键字的行），可以用 awk：

awk '
  /prices_std_dev/ {print; getline; print}  # 打印匹配行及下一行
  /另一条件/ {print}                        # 额外打印另一条件的行
' /home/debian/tmp/logs/binance.log

方法 3：sed（按行处理）

sed -n '
  /prices_std_dev/{p;n;p}  # 打印匹配行及下一行
  /另一条件/p              # 打印另一条件的行
' /home/debian/tmp/logs/binance.log

示例场景

假设日志内容如下：

2023-01-01 数据A
2023-01-01 prices_std_dev: 0.5
2023-01-01 数据B
2023-01-01 另一条件: XYZ
2023-01-01 数据C

运行命令：

grep -A 1 "prices_std_dev" binance.log | grep -A 1 "另一条件"

输出：

2023-01-01 prices_std_dev: 0.5
2023-01-01 数据B
2023-01-01 另一条件: XYZ

如何选择？

• 简单条件 → 用 grep + 管道（方法 1）。
• 复杂逻辑 → 用 awk（方法 2）。
• 需要更灵活的行控制 → 用 sed（方法 3）。

If you want to print another condition line after grep matches the target line (such as "prices_std_dev"), you can do it in the following way:

Method 1: grep -A + pipe + grep (recommended)

grep -A 1 "prices_std_dev" /home/debian/tmp/logs/binance.log | grep -A 1 "another condition"

Effect:

1. First match "prices_std_dev" and output the line and the next line (-A 1).

2. Then match "another condition" to the result, and output the line that meets the condition and the next line.

Method 2: awk (precise control)

If the conditions are complex (for example, lines that need to match different keywords), you can use awk:

awk '
/prices_std_dev/ {print; getline; print} # Print the matching line and the next line
/another condition/ {print} # Print the line of another condition in addition
' /home/debian/tmp/logs/binance.log

Method 3: sed (process by line)

sed -n '
/prices_std_dev/{p;n;p} # Print the matching line and the next line
/another condition/p # Print the line of another condition
' /home/debian/tmp/logs/binance.log

Example scenario

Suppose the log content is as follows:

2023-01-01 Data A
2023-01-01 prices_std_dev: 0.5
2023-01-01 Data B
2023-01-01 Another condition: XYZ
2023-01-01 Data C

Run command:

grep -A 1 "prices_std_dev" binance.log | grep -A 1 "Another condition"

Output:

2023-01-01 prices_std_dev: 0.5
2023-01-01 Data B
2023-01-01 Another condition: XYZ

**How ​​to choose? **

• Simple condition → Use grep + pipe (method 1).
• Complex logic → Use awk (Method 2).
• Need more flexible line control → Use sed (Method 3).